Introduction Antenna is final device for sending any information from your transmitter. In fm transmitter you need signal transmitted to any direction so you need antenna type that transmitted with polarized circularly. Antenna gain -3.2 dB, bandwith 500 KHz with maximum power handling 500 Watts. In order to use antenna on 88-108 MHz, broadband antenna type must be designed with no tune involved.
Signal Amplification Amplification of signal to transmit based on antenna gain in Decible. Signal from transmitter be able to doubled, tripled or even become more power. The value is called ERP (Emmittion Radiating Power). For Doubled your transmitter power to be ERP Power need stacked 4 antennas (3.12 dB gain antenna), 6 antennas (5.12 dB), 8 antennas (6.4 dB). ERP = Transmitter Power x Antenna gain.
Yes, it is Pirate Radio and yes, We are The HAMs, We are proud to be not a hobby, but Emergency Service. I confirm. Don't shoot me, please. I've just read a short message about this station on the Irish Paul's blog and I recognized The Radio when I met. Even without LCD.
6P7S (6П7С) TV sweep tubes, as their western sisters 6BG6 was used as a horizontal driver in some early black'n'white TV sets. In fact, this tube is not a direct 6BG6 clone, it is an octal modification of G-807 tube, which one was soviet clone of famous 807. Interesting, that both 6P7S and 6BG6 tubes has the same pinout and nearly the same characteristics.
I heard that 6BG6 valves sounds much better than 6P7S in audio devices and that 6P7S is worthless audio tube, much worse than G-807 and 6P3S ones. At the other hand, I heard that 6P7S has a beautiful clear treble, better than 6P3S. I'm not quite sure - it's just rumors.
As for me, 6P7S is a good choice if you have to put something more powerful than 6P3S (6L6) into the octal socket. Strangely, but 6P7S tubes are rarely used in HAM-radio (compared with G-807 and 6P3S).
Several days ago I listened to the completely empty ten meters band. There was a lot of noises, quiet CB chewing and nothing else. Suddenly I heard a slow, quiet, but very clear telegraph code, resembling W1AW QST. I have not heard the beginning, but wrote all heard:
..Santa placed tubes on the sockets and lit it. The soft red glow from its ones tiny heaters brightened the room. "The glow of the valves represents how man can show his thanks for the gift of God's Son that Christmas Eve long ago. Teach the novices to let their lamps shine before men that all may see it and glorify God. This is what is symbolized when the red lights shine on the twilight around the world like hundreds of bright, shining candles, each of them representing one of God's beloved radio amateurs whose signals are sounding for all to hear."
"Yes, red glowing" said Santa, "is the first color of Christmas." He pointed to the Rudolph, Red-Nosed Reindeer. "But the second color is green" Santa reached into his bag and pulled out Magic Eye tube and set it into the socket. "Teach novices about Magic Eye. Green is the second color of Christmas. The stately evergreen with its unchanging color represents the hope of eternal lif.....
At this point I lost to hear mysterious broadcast, only a few dits and dashes appeared in the noise, someone laughed quietly and that's all. But I realized that I have to add something green to my radio. I went to my attic and found a Magic Eye tube in my junk box.
MAGIC EYE TRANSMITTER HOWTO It is easy to install 6E5 on the place of oscillator tube because socket's pinout of this amazing valve is nearly the same to pinout of common 6J5 and 6C5 triodes. So, you can replace these tubes with The Magic Eye without any soldering. But if you want to see The Legendary Green Glowing, you have to apply some voltage to the Pin #6 (fluorescent screen). It will not affect the excitation or amplification, this electrode do not cross the main electronic stream in the tube, so it is unecessary to use a regulated voltage in this circuit. Let me demonstrate:
As you can see this is my last year's SKN MOPA transmitter with some minor changes.
GK-71 (ГК-71) is a somewhat similar (but not the same) to the famous 813 by RCA. There was another soviet replica of RCA 813 - GU-13.
GK-71 (ГК-71) has a narrower frequency range and a slightly less gain than, say, GU-13 tube, but there are some advantages - it was dirt-cheap and has a terrific endurance (resultant of massive graphite anode block and durable heavy-duty construction).
Possible, GK-71 was the most popular power tube in the AM pirate's masonic fellowship. I'm not quite sure, I have no statistical data of pirate's preferences, but all of my unsocial friends was a GK-71 fanatics.
At the other hand, this power pentode was a "Full Legal Limit" tube for the HAM radio amateurs and one GK-71 final have to be approved without power measuring. There are many fairtales about the one GK-71 tube multy-megawatters, asbestos glove for quick tube replacement etcetera, but reality is slighly less wondrous - 350 watts from one tube without overheating, up to 450-500 watts if you are out-and-outer.
The past two weekends gave me a chance to get some more operating time on my 1928 Hartley transmitter. These were the weekends of the AWA Bruce Kelley Memorial 1929 QSO Party . The first weekend I used my HRO Sr with the Hartley. On the second weekend I paired my Drake 2B with my Hartley. I had a good time working other '29 transmitters in Minnesota, Wisconsin, Illinois, New Hampshire, North Carolina, Ohio, Ontario and British Columbia.
In total I made 16 contacts and learned a little about the limitations of my station. First, I really need a higher antenna. My antenna is a 105' inverted "L" only about 10' to 20' off the ground. It loads up nicely but, given this low height, has a fairly high angle of radiation. It probably qualifies as a Near Vertical Incident Skywave (NVIS) Antenna. Out of my first six contacts, five were here in Minnesota and most of them reported a strong signal. I also found that the best time was late afternoon, not the night time hours. The first weekend the only QSO I had outside of MN was with Ohio and it was when the QSO Party rules allowed me to crank the power up a little. When the propagation changes my antenna works OK but I feel it does limit me. Next, I learned that 40 meter transmitter performance is a little down from 80. While I've received a good signal report on 40, I can't get as much power out and I had more trouble getting on frequency. My Hartley is a usable 40 meter transmitter but 80 is definitely its better band.
GU-50 (ГУ-50, folklore HAM name "poltinnik" meant "half-a-buc") was an universal, most common xUSSR power tube from the 50's up to the present days. It could be found in an every technical shop everywhere and was so inexpensive, in an usual TV-set's tubes price range. So funny, but sockets for those halfbucs was so rare and priced much more.
These power pentodes has been used as a transceiver final (one or pair of ones in parallel), in a modulator for the more powerful tube in AM transmitters, in a driver stages and (when SSB times comes) in the most common general class amplifier - three (or four) GU-50 in parallel with all grids connected to the ground.
GU-50 is russian version of WWII LuftwaffeLS 50 general purpose HF power pentode by Telefunken, also known as RL 12 P 50 tube in Wermacht's transmitters. Main difference between russian and german versions - socket's construction and dimentions, so I'm not quite sure that it is possible to use russian GU-50 as a spare part for a vintage german transmitter.
There are several other members in this family, such as DDRSRS 552 M tube, SL 152 (~12.6V filament) and EL 152 (~6.3V), but I don't know any more about these tubes, only that these tubes exists. READ MORE >>
Introduction
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