QRP2004 Build day 1

Here starts the log for the build today easy first day.

I'm creating the PCB and my process is to use press and peel film (Maplin AB15R) so I use the REVERSED images of the CU layer you can obtain either from the qrp2004 project team website (http://myweb.tiscali.co.uk/qrp2004/) or the yahoo group (http://groups.yahoo.com/group/qrp2004/files/) Printer is a laser doesn't work with an inkjet printer, Samsung ML-2240 and I am printing 1200x1200 dpi and as DARK as I can get it.
Make sure you check the print size is right. I used a 40pin DIL socket and couple 8 pin DIL sockets to check the sizes. Mine I had to print at 107% size. Print to normal paper until you get the size right.

Anyway I have 7 nice pieces of blue film ready to use.

It is still cold out so doing the rest of this in doors.... (except the etching)

1. Cut out 7 pieces of PCB sized to fit. Mine are slightly oversized.
2. Clean them of all grease and finger prints (I use Acetone and then fine wire wool and emery paper in a circular pattern). You end up with 7 shinny pieces of PCB. Now clean all the wire wool or emery paper remnants away
3. Iron on or feed the sheets and PCB through a laminator (I will be testing the later option on another build).
4. Allow to cool, peel off the film.
5. I use black marker (permanent) on the top ground plane side, you can use close fitting tape etc... your choice.

Outside now in shack...

6. Etch. You do not need a tank but I home-brewed one from a fish tank heater and aerator pump. I use either Ferric Chloride or some clear etchant. The home-brew tank I set the solution to 35degrees C and let it bubble away for about 35 mins and the boards are usually fine. Wash the boards with water and allow to dry.
7. You have a choice: either remove the etch resist pattern off the boards now or wait until after drilling the boards. I will tin mine (you do not need to) so will remove the etch resist and the tape or pen from the other side and I use a dip solution, you can tin too by chasing a bead of solder around the board (hint this is much easier when NOT drilled!). If not tinning and if you remove the resist the copper will tarnish quickly so you might want to use a flux spray like KS10.

Now the boring bit... drilling c900 holes! This might take a while.
I use a Dremel in a stand (the task is hopeless if not in a stand) with 0.7mm drill bit. Note some holes will need to be enlarged will cover those in later posts.
Drill all the 3mm holes for the mounting and the other 4-5mm holes for the TO220 and other transistors.

I think the drilling holes is why so many home-brewers have moved over to SMD...

I'll post some photos later.

You can use a photo resist and print the CU layer images to sheets and expose and develop etc... but I have not done it that way but many other homebrewers do.

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How to make a CW QSO

The original site at http://zs6ez.za.org/tutorial/cw-qso.htm has disappeared so I post that page here for reference for those trying to get started in CW.


A search for zs6ez on QRZ:
Born 1964, licenced 1980 as ZS6BCR. I've basically been inactive since 2000, due to other commitments. I hope to resume some ham radio one day. My main interest was in contesting, where I held several world and continental records in the single band category of CW, RTTY and Phone contests. I attended WRTC three times, as W6O, OJ1W and S572L. I ran a series of DXpeditions in the Eighties and Nineties, emphasising low band, WARC band and RTTY activity. You may have worked me from 7P, 3DA, A2, IH9, V5, ZS0 or ZS9. I also once did a bit of DXing, with 10BDXCC, 5BWAZ, 5BWAS and Top of the DXCC Honor Roll. I've slipped down a bit with the most recent additions, but maybe I'll get up there again one day. In the mean time, I'm working on my DXFC score (see http://dxfc.org) while flying business jets as a South African Air Force volunteer, playing with my daughter, holding down a real job, working on my PhD, managing a small group in our local church and running a flying school.


How to make a Morse Code contact...


The original is back up on a new site, here is email from Chris about it.
----- Original Message ----
> From: Chris R. Burger ZS6EZ <chris@********>
> To: Dominic Baines <dombaines@********>
> Sent: Fri, 31 December, 2010 1:02:57
> Subject: Re: Fw: [GQRP] Re: OT? Morse procedures...
> 
> > Other emails used all bounced...
> To this address，or did you use an  obsolete address？ I'm not aware of a
> problem with this address。
> 
> >  Please let me know if this is a problem.
> I would prefer if you linked to the  actual article：
> 
http://zs6ez.org.za/tutorial/cw-qso.htm
> 
> That way，if I  make changes they will show up。Also，Google is more likely
> to pick up the new  address if you link to it。
> 
> The original domain name disappeared，so I  suddenly had to establish a new
> one。 All the original content is  there。
> 
> Regards
> 
> Chris

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http://m1ktaipodamateurradio.blogspot.com/

Started something new today
http://m1ktaipodamateurradio.blogspot.com/

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2012 AWA Bruce Kelley QSO Party

The last two weekends I participated in the AWA Bruce Kelley QSO. Except for curious visitors, transmitters must be limited to 1929 (or earlier) designs and not crystal controlled.

This year I used my Hull Hartley at 10 watts input and a Drake 2B receiver. The change from last year was having a 80 mtr vertical available rather than a simple end fed wire. Unfortunately SE MN was under a blizzard warning for most of the first weekend of the party and I was busy elsewhere for most of the second weekend. Self excited oscillators like the Hull Hartley are prone to frequency wobble whenever the antenna load changes. My vertical swaying in the blizzard wind was too much for it. Rather than wobble all over the band I again used my 105' end fed inverted "L".

Even with only 3 watts out to a low (10' -15' off the ground) antenna I made 11 contacts and worked both east and west coasts. I had a good time.

Maybe next year I'll have an amplifier for my Hartley so that I can use the vertical (with the sway) and run closer to 6-7 watts out.

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QRP2004 Build

I have had a few questions about this project ( http://groups.yahoo.com/group/qrp2004/ for details) so I will start a build from scratch and blog it here starting in the new year (i.e. 2011).


This is the designed polyphase network for the QRP2004

Copyright © 2004 - 2005 by QRP2004 Design Team

The project design team include details of the design and method where you can look at options using different components (depending on what you have to hand), using different components the results are:
(RED) C=33nF, R (Kohm) 12,10,6.8,3.9,2.7,1.8,1
(BLUE) C=10nF R (Kohm) 47,33,22,15,10,6.8,5.6


See the project docs for details.

QRP2004 Web Site: http://myweb.tiscali.co.uk/qrp2004/

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JT65-HF - remarkable!

I've been using Joe Taylor's weak signal modes for a while now, mostly WSPR, but recently my attention has been drawn to an interesting spin-off which calls itslelf "JT65-HF".

Clearly many people have been there before me, as there is quite a bit of activity in this mode, which seems to be able to produce quite remarkable and astonishing results.

Having downloaded the software, set it up (easy peasy) and left it running for some hours, the resulting decodes have never ceased to amaze me, given the modest aerial setup I have here.

I presume that much of this is due to the "FEC" (Forward Error Correction) associated with this mode of transmission. Stations such as mine with modest capability therefore stand a good chance of getting their messages through, or conversely can successfully receive weak transsmissions from elsewhere to a remarkably high degree.

I would recommend anyone at least to have a look at this mode, and at what it can do.

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RF Decibel Meter

In any radio workshop, an RF decibel meter or power meter is an important instrument. Unfortunately, home-constructed ones are generally not sufficiently sensitive and/or are very temperature-dependent. These drawbacks are overcome by a device from Analog Devices which has recently become available: a low-cost DC–500 MHz, 92 dB logarithmic amplifier that enables an accurate, not too expensive to be constructed.

Decibel Meter Parameters
Frequency range:
100 kHz – 110 MHz with an error <1 dB
100 kHz – 200 MHz with an error ≤ 2 dB
Decibel range:
32 – 117 dBμ with an error at 10 MHz ≤ 1 dB
Scaling: 10 mV dB–1
Input impedance: 50 Ohm


RF decibel meter Parts List
Resistors:
R1, R2 = 100 Ω, SMD
R3, R4 = 10.0 Ω
R5, R7 = see text
R6 = 5.62 kΩ
P1 = 5 kΩ (4.7 kΩ) multiturn upright preset potentiometer
P2 = 25 kΩ multiturn upright preset potentiometer
Capacitors:
C1, C4 = 0.01 μF, SMD
C2 = 0.1 μF, SMD
C3 = 2.2 μF, 10 V, tantalum
C5 = 0.1 μF. metallized polyester
C6 = 10 μF, 63 V, tantalum capacitor
Integrated circuits:
IC1 = AD8307AN (Analog Devices)
IC2 = 78LO5
IC3 = CA3140E
Miscellaneous:
K1 = 50 Ω BNC socket for board mounting
Enclosure

RF Decibel Meter Description
The circuit diagram of the decibel meter stands out by its simplicity, which is due to the Type AD8307 monolithic demodulating logarithmic amplifier, IC1, from Analog Devices.
The measurand (quantity to be measured) is applied to pin 8 (INP) of IC1 via input socket K1 and capacitor C1. The capacitor ensures that no direct voltage can reach the IC. The second input of the IC, pin 1 (INM) is linked to the earth line via capacitor C4. The values of C1 and C4 are chosen to give a lower limit of the frequency range below 100 kHz.

Resistors R1 and R2 ensure that the input impedance of the meter is the usual value in RF equipment of 50 Ω. A parallel network is used to minimize any parasitic properties of the resistors. It is recommended to use SMT (surface mount technology) resistors.

The output of IC1 is essentially a current that causes a potential dropacross a 12.5 kΩ internal resistor which is available at output pin 4. Resistors series network R6-P1 is in parallel with the internal resistance to modify the scale factor, which is 25 mV dB–1 in the absence of an external circuit.

Capacitor C5 averages the output signal to ensure a stable display. Its value depends on the application: a larger capacitance gives a more stable, but slow, display; a smaller value is recommended for fast sweeping.

Preset P2 permits parallel shifting of the characteristic to give an attenuation of up to 14 dB or an amplification of up to 26 dB between the input socket and pin 8 of IC1, provided that R5 = 0. Resistor R5 provides a narrowing of this preset range.


RF Decibel Meter Display
The display may be a digital multimeter, but, although this is accurate, it is not easily calibrated.
A moving coil metering network with series resistor R7 facilitates recognizing any drift such as encountered, for instance, during calibration, but does not make reading it easy.

Measurements with sweep frequencies can, of course, be displayed on an oscilloscope. The decibel meter outputs a direct voltage that is directly proportional to the input signal. The display is calibrated in dBμ (decibel referred to 1 microvolt). The scale factor is 100mV dB–1, so that an input signal of 100 dBμ results in an output voltage of 1 V.

Radio Decibel Meter Construction
The meter circuit is best built on the printed circuit board, but this is not available ready made. As mentioned earlier, some of the components should be SMDs (surface mount devices) as specified in the components list. If the circuit is constructed on prototyping board, standard components may, of course, be used. Keep all wiring as short as possible, however.

If operation up to 30 MHz only is needed, IC1 may be inserted in a socket, but for use at higher frequencies the circuit should be soldered directly on to the board. This is best done after all other components have been fitted and the board has been checked thoroughly. This measure is to protect the AD8307, since this is not a cheap component.

Since the meter is an RF unit, it is clear that it should be fitted in an earthed metal enclosure. The power supply should, of course, not be fitted in the same enclosure. Another important aspect is that the 9–15 V supply voltage should be ‘clean’. It is advisable to use feedthrough capacitors at the power line inputs and measurement output.

RF Decibel Meter Calibration
The meter circuit should be calibrated with a suitable RF signal generator or, in an emergency, an AF signal generator with calibrated attenuator. Apply a signal at a frequency of 10 MHz and a level of 60 dBμ (1 mV r.m.s.) to the input of the meter circuit. Using a digital multimeter, measure the voltage at pin 3 of IC3, increase or reduce the output of the signal generator by exactly 10 dB and turn P1 to cause a change in the multimeter reading of 100 mV. The absolute value of the output voltage is not significant.

Next, apply a signal at a level of exactly 60 dBμ to pin 8 of IC1 and turn P2 until the meter indicates 600 mV. If the requisite equipment is available, the calibration process can be repeated at a number of frequencies for greater versatility of operation.

If a signal generator is not to hand, adjust P1 until the resistance between its wiper and earth is 1383 Ω measured with a digital multimeter. Finally, adjust P2 to obtain a voltage of 1.627 V at pin 5 of IC1, again measured with a digital multimeter.

Source: RF decibel meter

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80 Mtr Vertical Performance

I wondered if my 80 mtr top loaded vertical is a good antenna for the Bruce Kelley Memorial 1929 CW QSO Party. Part of the loading is the top 6' of two of the guys. Any sway at all causes a guy to sag a little shifting the load my Hartley sees. This causes my signal to FM/wobble...distracting to say to least and aggravating if the band is crowded. I needed to know if the gain offered by the vertical over my endfed wire was enough to outweigh the the wobble it introduced.

The reverse beacon network at http://www.reversebeacon.net/ allowed me to get a good idea of real antenna performance. All I had to do is call CQ and any reverse beacon stations hearing me automatically posts my call, frequency and signal strength to the web. By switching between my low endfed wire and my vertical I could get a good A vs B comparison. By doing this over a period of time I could see how changing nighttime propagation impacts this comparison. Monday night I did exactly this and then sorted though the data to see how the two antennas compare from about 8PM (2:00 UTC) through the next morning.

What I found was that for the east coast (PA) the vertical offered 4-5 dB gain throughout the night. While not a spectacular performer it is almost always better than my endfed wire...but signal reports all mention the wobble/FMing introduced by antenna sway. Based on this I'll stick with my endfed wire for the early evening hours and then switch after about 10PM when the band activity dies down a little.

For next year's Bruce Kelley QSO Party it would be nice to have this problem solved by building a '29 style amplifier to use with my Hartley. Fortunately my 1934 transmitter already has an amplifier stage in between the oscillator and the antenna. My vertical will work fine with this transmitter during the AWA Linc Cundall Memorial CW Contest in January.

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Mag Loop

Just posting this as not QRT.

The WX here in Mechelen (Belgium) had been snowing for the last week. So I have taken a mag loop antenna built by Clive (M5CHH) (from G4TPH design) I have put it up suspended in the open door way out to the patio.

I determined that the door was 100% uPVC not metal framed and there does not appear to be any chnage in coupling with the door closed or open. The sealed windows are some metal looking but doesn't seem to effect the loop.

Just thought you might like to see these:

This is the loop on 40m :-)



This is the loop on 30m :-)

This is the loop on 20m :-)

I am about to go out to find a place were I can get some AA batteries for The 30m QRSS beacon I obtained from Han (G0UPL) and Steve (G0XAR). So hopefully ON/M1KTA should be QRV on 30m shortly.

The land lord still will not allow an external antenna so this looks like a good option.

BTW the pictures grabbed from MiniVNA Java software. Putting it on a contunous loop makes tuning dead easy.

Not tried a different balun that will give me 10m yet. I used 10 x 400mm legs to make up the loop. I'll post a photo soon.

I'll run it with the FT817 later.

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Broadband PLL FM Transmitter 88-108 MHz

Here's a simple FM transmitter design. It uses pll circuit from Motorola MC145170. This PLL includes the prescaler and a serial standard bus called SPI. We advise to use the P2 version that fixes some init issues during the Power Up.


PLL FM Synthesizer
This PLL circuit is definitely smaller than the old one, consequently we've added on the radio board, the power control circuit that allows to switch on, the RF signal when the lock detect is established. In fact a simple LM317 that supplies the last RF stage, is controled by the lock detect signal through the ADJ pin.

The oscillator and the RF driver stages have been improved to get a better harmonics rejection than the previous version. We have replaced the BB204 varactors by new ones: BB209. Consequently, the kvco is more stable on the FM band and the AF signal has been directly applied on the control voltage line coming from the PLL. A Cauer filter has been added to improve the second harmonic rejection.

Digital Board 16F84
The digital board uses a 16F84 Microcontroller to drive the FM transmitter equiped with the MC145170 pll circuit. The pic is in charge of controling the SPI Bus in order to provide the 205 channels of the FM band.

Two keys allow you to launch a scan frequency through the FM band with a 100KHz step frequency and also a storage operation into the EEPROM. When the frequency setting is achieved,the pic controls the lock detect signal to prevent radio hardware issues.

The schematic is quite simple ,consequently it's not really necessary to provide technical explanation concerning the design. The lcd display is a 2*16 caracters with backlight. Download FM Synthesizer Schematic (pdf) - Digital Board Schematic (pdf) -  Digital Board Hex.

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ROPOCO SSB - a selfish rant

I will be the first to admit that this is a very selfish point of view, but I really am quite annoyed (well as annoyed as I will allow myself to be over something which is a hobby/leisure activity) that the "powers that be" whoever they are, have turned one of the twice-yearly ROPOCO contests from a CW challenge to an SSB or phone one.

Especially ROPOCO1 (April) in which I have previously participated many times.

I am not a contester at all, but I really enjoy this particular challenge as it is, quite frankly, just that, a challenge.

What it challenges, from my own selfish point of view is one's CW sending and receiving ability/technique.

It does this in quite a different way to that of most if not all other contests in that _ACCURACY_ is prized above all else.

Most other contest have so many elements which are predictable (report, serial number, region, and so on) that "quantity" rather than "quality" carries enormous weight, whereas in ROPOCO accuracy is king.

Sending technique and accuracy is challenged. In other forms of amateur CW communications the odd sending error is normally of little consequence - the operator who knows he has made a mistake in transmission has to decide whether or not to correct that mistake, and if he decides to correct it, he has numerous methods open to him how to achieve that. In CW conversation, he will often just let the mistake go and rely on the operator at the other end picking up the error and dealing with it in his own way.

With ROPOCO this concept just doesn't work, and the challenge is for both the operator sending, and the operator receiving knowing how to deal with what they think might be a mistake in either transmission or reception. Mistakes lose points!

If you have never participated in ROPOCO this notion might be somewhat lost on you, but those of you who have will know exactly what I mean.

It could be argued, and I am sure that it will be, that this format should translate perfectly well to a "phone" format, and I am sure it will, but my point is that the corresponding challenge in speech communications is quite different to that in telegraphy.

For my money, I "they" wanted to try out ROPOCO in speech form, they should have had an _extra_ contest for the speech boys and left us brass pounders with our twice-yearly bout of fun.

The reason why I am so narked that the April test has been changed is simply because that is the one I usally participate in!

How selfish is that?!

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2 Channels RF Remote Control-Transmitter Receiver

This RF remote control is useful to handle some electric device. If you want to control your garage door, the only way is to use some RF remote control. The transmitter-receiver circuit use few components and ordinary. It's easy to build it because you don't have to tune-up any coil or variable capacitor. The RF modules are fix to work in 418MHz area.

Remote Control Design Consideration

• The check of the received data because many other devices are working in this frequency (418MHz)
• The power-saving of the transmitter. One transmitter must have battery long-life, there is not good to change the battery after 3 days ;) . I don't care about the receiver`s power supply, because receiver must be working all the time.

Remote Control Features:
Transmitter

• Standby: <1uA (less than 1 microampere)
• only 3v power supply
• 10...15m distance range
• 2400bps communication
• 2 initial bytes for device recognition (ID bytes) calculate the checksum of the sended data (to avoid fake commands)
• few components
• small size

The transmitter is constituted by AT90S2323 microcontroller and TLP434 RF transmitter module at 418MHz. I have designe the transmitter for more battery economy and safe transmition of the data.

• The battery economy is made it by the use of powerdown mode of AVR. In this case the AVR goes to sleep with less than 1uA (microampere) current and wait for external interrupt on pin PB1 to awake from sleep and continue operating.

1. If you press the S2 key, the logic of this pin goes to '0' (0V) and AVR awake frome the sleep mode (because PB1 is INT0) and check if pressed the S1 key. If not, the AVR take as pressed key the S2. If yes the AVR take as pressed key the S1. If you press the S1 key the logic of this pin and PB1 (through 1N4148) goes to '0' (0V). In this case the AVR take as pressed key the S1.
2. After, calculate the checksum and transmit 4 times the same 4 byte sequence to make sure that receiver takes the data and goes to sleep mode until next interrupt on PB1. When the INT0 pin (PB1) of AVR goes to 0V, the transmitter TLP434A is working. If you stop press the switch S1 or S2, the TLP is stop working.

• The safe transmition of the data based to transmition of 4 bytes with serial form at 2400 bps (bits per seconds). 1st and 2nd byte are for recognition of valid remote control from receiver (like ID bytes), 3rd byte is command byte. The relays status dependet by the value of this byte. Finaly, the 4th byte is the checksum of the earlier 3 bytes.

This transmitter will work with all 2323 chips but better is AT90LS2323 with working voltage 2.7 - 6 volts.The microcontroller that I use is AT90S2323 with working voltage 4 - 6 volts. Its worked fine with 3v lithium battery.
As antenna you can use ~7cm cable in to transmitter`s box

Receiver

• Hardware UART at 2400bps
• 4 bytes (32bit) length communication
• checksum of the received bytes (to avoid fake commands)
• few components
• smal size

The receiver constituted by RF receiver module RLP434A at 418MHz, the microcontroller AT90S2313 and the 2 relays with can handle any electric (or electronic) device up to 10 Amps (the contacts of my relays are 10Amp at 250Volts).

The RLP434A is an RF receiver module with receipt frequency at 418MHz with ASK modulation. There are 2 outputs from this module, the digital, with levels from 0v to VCC (5 volts in our case) and the analog output. Analog output is not used. The transmitter send 4 bytes with 2400bps 4 times and the receiver RLP-434A, collect them and move them to AT90S2313 to RxD pin, PD0.

Two reasons to select AT90S2313 (20pins) instead of AT90S2343 (8pins) is because

• AT90S2313 use a hardware UART adjusted at 2400bps and the hardware UART is more stable, with smaller code, than software UART that I use in the transmitter. If some serial data arrive at the middle-time of some other routine other than receive routine, for sure we will loose this bits of data. The hardware UART does not have this problem because have buffer for this (UDR register). This is what I mean that the hardware UART is "stable".
• With AT90S2313 we can drive up to 14 relays with future upgrade of the firmware, one relay to each pin.

As antenna you can use a cable 30 - 35cm long

Power Supply for Receiver
The power supply of RF receiver constituted by 2 voltage regulator, LM7812 and LM7805. The first (12V) its only to power the 2 relays and the 2nd (5V) to power the AVR microcontroller and the RF receiver module. The LED, is voltage indicator and the 4 capacitors are to flattening the voltage.

Usage of Ttransmitter
Power on the receiver and press S1 key to transmitter. You will see that relay on PB0 of receiver will arm. If you press one more time the same key, the relay will dissarm. If you press S2 key from transmitter you will see that relay on PB1 of receiver will arm. If you press one more time the same key, the relay will dissarm. Each key is for 1 relay only.

I choose to drive 2 relays and not only 1 because for some application like garage door 1 relay can handle the door (open-close) and the other to turn-on or off the light of the garage.

Click here to download the firmware, source code and schematic for AT90S2313 and AT90S2323 microcontrollers

The RF modules TLP434A and RLP434A are from Laipac

Source: 2 Channels RF Remote Control

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8W Broadband RF Amplifier 2SC1971 88-108 MHz

Here's a broadband FM RF amplifier using 2SC1971 VHF power transistor. The RF Amplifier PCB layout designed for FM broadband 88-108 MHz using microstripline technique. This 8W RF amplifier circuit provides an appropriate power boost with an input of 500 mW.

RF Amplifier PCB
The PCB outline is 77 x 56 mm use FR-4 double sided photoresist epoxy pcb material for best results.

RF Amplifier Construction
All SMD components are 1206 types. Connect the bottom layer (groundplane) on several points (through via's) with the top layer of the PCB.

Note:
CuL = magnetwire, enameled copper wire
- 1 mm equals approx. to #18 A.W.G
- 0.8 mm equals approx. to #20 A.W.G
- 0,3 mm equals approx. to #28 A.W.G.

• All diameters are measured from the inside of the coils, i.e. 'internal' diameter.
• Make sure to mount the rf-transistor on a appropriate heatsink and use some thermal heatsink compound between the flange of the transistor and heatsink! (Thermal resistance heatsink at least 6°C/W.)
• All parts are soldered directly on the toplayer of the PCB.

Source: Amplifier 6Watt MicroStripline (2SC1971)

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Classic RF Probe using 1N34A Diode

One of the handiest accessories you can have around the shack is RF Probe. It can be used to measure RF voltage (and power), trace RF signals in a new design, and troubleshoot malfunctioning RF circuits. This RF probe is easy to build.


Complete Classic RF Probe Schematic

For best probe accuracy, size the resistor to match your DC Voltmeter's input impedance:
R = 4.7 Meg for Zin = 11-Meg;
R = 4.3 Meg for Zin = 10-Meg;
R = 430 K for Zin = 1-Meg;

Source: Classic RF Probe

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BAS70 RF Probe Circuit

This RF probe is useful for small RF power levels up through the microwave frequency bands, and simply connects to your DVM (Digital Volt Meter). The voltage shown will not be accurate, since this is a rectifier probe (diode probe), but the measurements are good enough for you to be able to determine where the RF stops, or if a stage is not giving the gain you think it should.

RF Probe Schematic

RF Probe Notes:

1. Maximal rated power is defined by 50 Ohm resistor (use more resistors connected in parallel) and maximal reverse voltage of diode. (for BAS70 70V)
2. Compute output power from measured voltage:

Pout=(( Vmeasured + 0.35 V ) / 2^0.5 )^2 / 50

where:
Vmeasured is RF probe output voltage.
0.35 V is diode forward voltage (actual for BAS70)
/ 2^0.5  is peak to effective voltage
50 is load impedance

Source: RF Detector / RF Probe

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4 Ports Power Splitter 2.4 GHz

Here is a device called a power splitter (divider/combiner). You can use this to phase four antennas together for increased gain or combine the input/outputs of amplifier for increased power.

This 4 to 1 (4-1=4 ports) power splitter work at 2.4GHz. You will use it for stack 4 pieces of 2.4 GHz helical antenna for get 6 dB more gain on AO-40 satellite down link receive.

Power Splitter Schematic and Printed Circuit Board (PCB)

Source: 2.4GHz 4 to 1 Power Splitter

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RF Field Strenght Meter with Attenuator up to 200 MHz

The RF field meter unit will be in great help to tune transmitters for best performances. You can measure the radiated energy field and can easy tune the system for max output field strength (maximum power).

RF Field Strength Schematic
This field strength meter with selectable attenuator. You can used it for measuring the antenna gain and pattern, compare different magnetic field strength. See the following RF field strength meter schematic.

RF Field Strength Features:

• Input Terminal: SO-239 (M type) or BNC
• Output Display: Analog power meter modify from a 50uA current meter and after calibrate with a RF generator.
• Measuring Range: From +3dBm to -35dBm with attenuator. (0dBm = 1mW at 50ohms)
• Operating Frequency: 100kHz to 200MHz
• Power Source: No need.
• Attenuator Range : With 6 ranges (0dB, 3dB, 6dB, 9db, 12dB, 15dB)

Source: Field strength meter with attenuator

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100W RF Power Amplifier 50 MHz 2SC2782

This is a 6m band RF power amplifier (50 MHz) with 100W output. It used with my FT-736R and drive from 10W for the 6m SSB DX. The Building information comes from Japan CQ Magazine. The Toshiba RF bipolar power transistor will be used in it.

RF Power Amplifier Schematic and PCB

Grounding
If you want to construc this rf amplifier, it's the better way if the double side PCB use for increase the grounding and current transfer. The TX power can be tune to 120W.

RF Amplifier features:

• Input Power: 10W
• Output Power: 100W
• Operating Frequency: 50-52MHz
• Operating Mode: FM- SSB
• Operating Voltage: 10-16V DC
• Operating Current: 12A DC for 100W RF output
• TX trigger:

1. Trigger by internal RF power input detection circuit.
2. Trigger by external equipment trigger output.

Download information (Japan CQ Magazine) page 1 page 2

Source: 6M 100W RF Power Amplifier

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80W RF Amplifier 2SC2782 88-108 MHz

This is a RF power amplifier design using 2SC2782 bipolar transistors in a tuned class C circuit. The amplifier can be driven to full power with less than 1 watt driving power, so that a large gain margin results in this FM transmitter.

To obtain stability in this rf amplifier, I employed several techniques, such as placing the resonances of base and collector chokes far apart, damping the chokes with resistors, using RC combinations for absorption of unwanted frequencies, using feedtrough capacitors for bypassing on the board, etc. It took some tweaking, but the amplifier ended up unconditionally stable.

RF Amplifier Low-pass filter
This amplifier has a low-pass filter at the output, resulting in a signal clean enough to be directly connected to an antenna. The SWR meter was placed before the filter, in order to clean out the harmonics produced by its diodes. In any case, while the signal is clean enough to easily satisfy usual legal and technical requirements, this transmitter should not be used at a multi-transmitter site without further narrow band filtering!

This is so because any other strong signals on nearby frequencies would be picked up by the antenna and coupled to the power transistor, which would mix it up with the own signal, creating a wide array of intermodulation products, some of which would be re-radiated! This is a common and very big problem in many multi transmitter sites. In such places, not even one FM transmitter should be allowed on the air without narrow band filtering! Such filtering is easily accomplished by means of a single tuned cavity, which can be constructed from copper tubing or sheet.

RF Amplifier PCB

Here is the PCB layout, including the microstrips. The board is 20cm long and is double-sided, with the backside being a continuous groundplane except for two small pads at the driver transistor base and collector. I cut out these pads with a knife, rather than making a whole computer drawing for that!

Source: RF Power Amplifier 80W 2SC2782

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