AWA Linc Cundall OT CW Contest (Part 2)

The second half of the AWA Linc Cundall OT CW Contest was this past weekend. Between Saturday evening and Sunday afternoon I added 4 contacts to my log including W0LGU(MN), WA9QNN(WI), WB9WHG(MN) and NG9D(IL). While not a lot of contacts this year my push-pull 6L6 transmitter seemed to work pretty well. I suspect my low antenna (only 10-15ft off the ground) resulted in a lot of RF going straight up. I did OK for nearby stations but heard/worked no east coast stations.

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AWA Linc Cundall OT CW Contest

The first half of the AWA Linc Cundall OT CW Contest ran Wednesday evening through Thursday late afternoon. This coming Saturday is the second half of the "contest".

My station this year is a 1938 vintage NC-101X and a homebrew crystal controlled push-pull 6L6 oscillator. Electrically this transmitter is based on the QSL Push-Pull in QST, June 1940. I added cathode current metering, a load control and regulated the screen voltage to 150V. I ran mine with only 300V on the plates for about 20 watts input and around 10 watts output on 80 and 40. Cosmetically this transmitter is based on what I had on the shelf to work with, an old amplifier build in an even older Meissner Signal Shifter cabinet.

Here in SE Minnesota using my low hung 105' inverted "L" antenna I heard no AWA stations on the air Wednesday night but did work W0NYQ(MN), KB0ROB(MN), VE3AWA(OT) and AA9DH(IL) late Thursday afternoon.

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14W UHF TV RF Amplifier 470-860 MHz

Working Frequency 470-860 Mhz UHF Band IV and V. Power out of the RF Amplifier about 14 Watts with power input 1.5 Watts.

( Transistor Datasheet)

Schematic

Part Lists:
C1 = C6 = C16 = 4,7 pF (500 V) multilayer ceramic chip capacitor
C2 = C3 = C20 = C21 = 33 pF multilayer ceramic chip capacitor
C4 = C9 = C13 = C19 = 1,2 to 3,5 pF film dielectric trimmer
C5 = C7 = C15 = C17 = 100 nF multilayer ceramic chip capacitor
C8 = C10 = C11 = C12 = 220 pF multilayer ceramic chip capacitor
C14 = C18 = 6,8 mF/40 V solid aluminium electrolytic capacitor
C22 = C23 = 1 pF (500 V) multilayer ceramic chip capacitor
L1 = L2 = L13 = L14 = Coax. 50 Ohm with diameter 2,2 mm; lenght 29,0 mm, soldered on striplines
75 W (1,1 mm ´ 28,0 mm). inner L1 dan L13 not connected
L3 = L4 = 52 W stripline (2,0 mm ´ 16,5 mm)
L5 = L8 = 470 nH microchoke
L6 = L7 = 39 W stripline (3,1 mm ´ 8,0 mm)
L9 = L12 = 1 Turn (1,0 mm); diameter 5,5 mm; lead space 2 ´ 3,5 mm
L10 = L11 = 39 W stripline (3,1 mm ´ 34,0 mm)
L3, L4, L6, L7, L10 dan L11 are striplines on PTFE fibre-glass PCB wirh dielectric (Îr = 2,74); w 1/32".
R1 = 10 W carbon resistor

BIAS CIRCUIT

Component Part List:
C1, C2, C4, C5, C6 = 1nF LCC Chip + 10nF LCC Chip
C3 = 100µF Sprague
C7 = 10µF Sprague
D1 = 1N 4001
L1, L2 = 5 Turns , Diameter 0.5 mm, W Diameter 3mm
P1 = 1k.
R1 = 56 ohm/ 1/2W
R2 = 5600 ohm, 1/2W
R3 = 2.2 ohm, 3W
R4, R5 = 56 ohm, 1W
R6 = 4,7 ohm, 1/2W
T1 : BDX 54 B/BD139

Component Layout


PCB Dimension 145,74 mm X 59,865 mm

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RF Amplifier Protector Circuit

This circuit protector is so simple, but it has big function in protecting your rf amplifier device. There are three kind of protect : heat sensor, DC forward - reverse and input over drive. If the input signal more than threshold limit, relay will engaged to disconnect power supply voltage.

The input part signals for protecting are :
* Termo Switch (Heat Sensor Resistance) from your active component, RF Power transistor/FET.
* Forward and Reflect (reverse) from your directional coupler after your Low Pass Filter Output.
* Over Drive from directional coupler at the input of your rf amplifier to limit power input in normal condition.
* Relay (12v DC) for disconnecting power supply of your RF amplifier if condition for protecting happened.


Attention> :

Do it manually before you install it in real condition. Don't forget to adjust 50K resistor for every input parts.

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VHF TV RF Signal From AV Sources.

Small Circuit to send your Audio Video from DVD player or satellite receiver to VHF RF signal. This circuit connected to TV RF input via 75 ohm cable or telescopic antenna. Don’t use this circuit for more power without filter and use antenna only to transmit. Frequency range on vhf band about 50-250 MHz.

You can change the transistor for transmitting on UHF band. Keep the components lead shortly. Recommended use crystal or PLL technic for stability of frequency.

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An Iambic keyer rated for cathode keying

When using my vintage transmitters I've missed not having a keyer. Many older tube transmitters are cathode keyed. The voltage across the key terminals can be high enough to fry the output transistor of a typical modern keyer. In some cases the voltage can even be high enough to be a safety problem.

I already had a K1EL K10 keyer board ( http://k1el.tripod.com/K10.html ). I added a Keyall from Jackson Harbor Press ( http://home.att.net/~jacksonharbor/keyall.htm ) to make a keyer capable of keying up to 500V at 2.A. It works great! I even installed a jack for a straight key so that I use the K10 CW monitor plus the Keyall isolator on Straight Key Night.

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How To Stack FM Broadcast Antenna

Stacking your broadcast antenna will make your antenna have more gain. If your antenna have more gain, more ERP (Emmittion Radiating Power).

What do you need for stacking antenna?

- More antennas that identical each others.
- Power divider to distribute your RF power to each antenna.
- Jumper cables to connect antennas

Stacking for 4 Antennas

Antenna :
Prepare 4 identical antenna. Tune the antenna for Matching on the working frequency.


Power Divider :
Prepare 1 power divider with 1 port input and 4 ports output.

Jumper Cables :
any length of coax cable with 2 N connectors to connect between power divider and antennas.

Determine Range between Antennas

When you install the antennas in collinear system, you must observe the distant “D” (see drawing of follow page) between two antennas.
The formula for calculate “D” is :

D = 0.75 x λ

Where :
0.75 = is the multiplicative coefficient;

300
λ = -----------
F(MHz)

SWR reading on the frequency 94.4 Mhz <1.25

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TV Linear Power Amplifier 470-860 MHz

The Wide-Band UHF Power Amplifier for TV Transposer band IV/V designed with transistor BLW32 and BLW33. In this case, my RF Amplifier design replaced them with 2 pieces BLW34 have good result.

RF Amplifier for 470-860 MHz taken from Philips Aplication Note (AN_BLW32_33). Please download file in PDF format.


For combine two BLW34 download file here

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Low Pass Filter For FM 88-108 MHz

Filter used for eliminate unwanted harmonic frequency at second and third. Notch filter, Band Pass Filter (BPF), and High Pass Filter (HPF) sometime combined in constructing LPF design.

Schematic below for FM Broadcast Lowpass Filter 88-108 MHz. It has been tested with a good result.

Note : Make the coils at 74 nH and trim them to adjust exact value.

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Antenna For UHF TV Transmitter

Description
Antenna used for TV Broadcast Antenna UHF Band IV-V and broadband for 470-860 MHz. . It's called UHF Panel Antenna. The UHF TV Antenna have gain 10 dB. It can be tripled or more the transmitter power. Tne antenna is packed with Radome to protect from ice or snow.

Dimension of Antenna and Radome

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FM Transmitter 88-108 MHz

Main device to transmit signal is transmitter and in broadcast FM is called FM transmitter. FM Transmitter divided by into three block :
1. Audio Processing Block
2. RF Generator (VCO+PLL) Block
3. Amplifier and Filter Block.

For covering 88-108 MHz, the transmitter must be wideband FM Transmitter. For stability Frequency output must be PLL FM Transmitter. For Long Range Transmission must be High Power FM Transmitter.

Below is FM Transmitter Product from BROADCAST WAREHOUSE, Model : ALLONE FM TRANSMITTER 1 WATT





Here is The Manual Technical with schematic.

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FM Amplifier 88-108 MHz

FM amplifier is used for amplify signal from exciter in broadcast radio station. In this page, RF FM Amplifier uses solid state material with minimum gain 9dB. Input of the FM Amplifier needs 5-10 watt with power output about 100 watt.



The Block schematic and datasheet

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Straight Key Night M.O.P.A. Transmitter

After reading a lot of ancient QSTs, ARRL and Jones Handbooks plus e-mail conversations with my friend, Louis VE3AWA about American depression-era style rig design, I decided to build a classic breadboard transmitter in time for Straight Key Night.


Well, breadboard MOPA seemed like a very
interesting idea, it was absolutely unusual for me - I never
used wooden chassis (breadboard) without any metal shielding before.
Second problem - I'd started this project too late,
for only one week before the SKN.
To my surprise, I got my firefly finished and fired-up during Straight Key Night! Without any success - there was no SKN participants over here. But what done is done and I was so glad to hear many "loud and clear" signal reports and heartwarming words from EU CW stations. Maybe next SKN, VE and W stations will make a sked to work UU1CC.
READ MORE >>

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