HFU HF Underground
General Category => For Sale / Wanted / Barter => Topic started by: Stretchyman on October 28, 2015, 0724 UTC
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:) Modified pricing on my 10W 6925KHz TX's.
$200
Complete, Tested, Boxed, Bargain!
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Looks like a good deal for anyone trying to get on the air at a relatively low cost.
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if I had the extra cash, id snag one.
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I've specifically designed and built these for the Pirate community and if your just starting out and thinking of broadcasting they are ideal in many ways.
1, Very easy to put together, if you can solder, you can build it, Yes they are small but why make them any bigger, PCB's are expensive!
2, Decent power O/P, 10W carrier and 40W peak will (with a decent antenna!) give good range, Less power is fine for experimenting and more power, well that's another story!
3, They can work on ANY frequency upto 8MHz
4, I can give you ALL the help you need in getting these things on the air and I can build the whole system if you really want me too but would prefer (it's much cheaper!) that you build it yourself.
I must be careful here as assume that folk who want to construct circuits are as competent as myself and realise this may not be so.
I've been in 'RADIO' all my life and have always wanted to build them, designing and selling these is a dream come true for me (REALLY!)
So I'm not going to sell you something I've spent the last 2 years of my life putting together to disappoint anybody, trust me on that one!
OK!
Stretchy.
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i use SN16913 to low level AM modulate and mix a local PLL 1PPM oscillator and from there, the mixed and AM modulated output goes to a LPF, LNA driver and another LPF, then its ready for a final RF amplifier tuned for the specific frequency.
think of it like reception in reverse, its real easy.
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OK, not familiar with that chip (SN16913) but looks similar to a NE602 et al.
You can direct mod a DDS which would be interesting and similar to your setup, see;
http://www.analog.com/media/en/technical-documentation/application-notes/AN-423.pdf
Good to hear folk are still experimenting and building!
:)
Stretchy.
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I've been building my own transmitters since 1980.
the easiest ones are made from fm/am car radios (pll controlled) by simply by changing the pll Crystal frequency from 10.7Mhz to 10.6Mhz (I use a variable cap) then using the LO output and modulating it from there.
then tuning the radio to 87.9 yields LO 98.5 output or 92.5 yields LO 103.1 output.
I've even modified an old 1980's era radio scanner to operate as a wideband transmitter.
everything that receives, transmits, albeit extremely low emissions without modifications though.
the best was when I was 13 on a school bus trip and the kid in the seat to my left was listening to the FM radio on his walkman, I took out my "modified" walkman and tuned around slowly until I heard his cut off (he had it loud on his headphones), I need not tell you that when I told him I was doing it, he got extremely mad, yelling like a child and tried valiantly to get the bus attendant to stop me but hey, I just have a walkman and I'm listening to the radio ;D
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Yep done the same with a single transisitor (somewhat simpler!) and done bogus radio shows for my local, 'I clean my car every day' neighbours, many a jolly laugh, Ha Ha!
Anyway we are departing from 'Advertising' my marvellous LuLu's.
I'm still to see a better or simpler design, i.e. 1 FET, 1 chip and 40W!
;)
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Great Story, Gotta add mine. in the 1963 I was in Junior High & smitten by a Popular communications "DIY" Article "Build a Home Brew 160 Meters Xmtr" and Built it, Had to also build a RF Signal Generator (Dad Bought me EICO Kit) (It was AM transformer) And finally got a Xtal from Oklahoma City, plopped my Radio on 1590 KCs, 10 Watts AM, I also had the Knight Kit Phono Oscillator, I could Turn Off Neighbours AM Radios listening to KAAY 1090 in Little Rock from a 1/2 Mile across the Cotton Fields around my house, then when they knew it was "Bernay" the 4 foot Handgrenade, They didn't Stomp me...I was the Hot Licks Guitar Kid in Saline County, Arkansas!
The off side was, whenever the local Sheriff or City Police had any Problem with their (35 MHz) Radios, I Was First Person Called, in case I was doing Mad Science on River Street! I was 14 Years Old. Had all kinds of Wires in the Elm Trees and Tall Oak Trees around the Home.
I Had read about a Pirate Radio Man who could not get Local Radio Stations to give him Air Time, in Pop'comm. He built his own Radio Station, got busted. He had written a book "Mytheology" I think he was in Ohio.
I became a Hater of Television when JFK was shot, I was watching on TV, and started building Knight Kit SW Radios, and became certain that "Television Was Why Johnny K Was Killed" I figured Nixon Lost because JFK looked Better on TV" therefore: Television was 666 Image of Beast!
Sounds Crazy for a 14-15 Year Old Kid.....well, it was. I am 66 Years old NOW & I know I Was Correct, in a Twisted Way, after my Family took me to Uncle Edward L. Bernays Furneal (He died at 103 Years) I study a little about Freud & My Uncle, & My Grandmother Was a Administrator of Recrational Therapy at VA Hospitals & State Mental Hospitals, so I grew up a Book Worm & Offish Kid, only 1/2 Jewish (Wrong Half) I had no Connection, no Bar Mitzvah , raised Epicopal, I Felt More Akin to the Voices on Short Waves, fom Far Wawy Places.....HCJB Quito Equidor, I Write Them for QSL.....put KITO, EQUIDOR on Enveloupe...LOL. I got QSL back anyway! I love radio, short wave radio. I have a 10 Meter Station (HTX100, Astron Power Supply, MFJ 931 Grounder, 1/4 Diaploe, but my Senior Apartemet is Inside Window into Well, All Building is Full of RF and Alumin Sidinf, I cannot even get 11 Meter RECEPTION, or AM BC Rception in my Aparment.
Why am I wriying all this? What is this FOERUM?
Of, LuLu Style 10 W Carrier AM Xmtr! Yeah...
I guess I am Oft Off Topic....(A PUN there!) My Old Brain is Lame....) Maybe Insane, Poets Often Speak in Thyime
Drunk of Wine, when Clocks Have No Time, DX is FINE! 73 de W5AWG
I've been building my own transmitters since 1980.
1980's era radio scanner to operate as a wideband transmitter.
everything that receives, transmits, albeit extremely low emissions without modifications though.
the best was when I was 13 on a school bus trip and the kid in the seat to my left was listening to the FM radio on his walkman, I took out my "modified" walkman and tuned around slowly until I heard his cut off (he had it loud on his headphones), I need not tell you that when I told him I was doing it, he got extremely mad, yelling like a child and tried valiantly to get the bus attendant to stop me but hey, I just have a walkman and I'm listening to the radio ;D
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Now complete, i.e. Built & Tested with 6930KHZ Xtal (will pull down to 6925KHz).
Contact me direct for usual 'HFUnderground ONLY' Discount!
Have some Mod Tranny's wound too so can supply EVERYTHING!
Let me know what you need.
Stretchy.
eBay item number:
131595757554
Stretchyman,
I'd be interested in having one of these totally built for me. I have an antenna here, but just don't have a soldering iron and the time or patience in putting it together.
Please contact me by email, walkerbroadcasting@gmail.com
Paul
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Final price reduction, I can't sell them any cheaper!
Have a few left.
$200 all in Inc postage.
Str.
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FCC loves strong signals on same frequency at a working hour clock schedule. 8)
SWL skill comes from really working for that catch. :o
Anybody can pull in 250kw and 20 db curtain antennas jobs. I am fascinated by WW2 and those little code key sardine boxes where if you were caught, you were SHOT!
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LuLu is very low power and FMs badly.
But, I assume one could remove crystal and install a suitable DDS.
The very low power really is a toy, but if modulator is clean , can be used for linear amp to perhaps 300 watts. The caution is, AB linear amps are only on average about 33 percent efficiency. So, obviously if you are using AM the pep will be 4 x carrier. The linear needs have balls to do 4 x carrier without becoming flat toped out.
The little rig I have FMs is useless really without a DDS, and could in principle be used to drive a linear to a practical, maybe 100-200 watts. :P
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LuLu is very low power and FMs badly.
But, I assume one could remove crystal and install a suitable DDS.
The very low power really is a toy, but if modulator is clean , can be used for linear amp to perhaps 300 watts. The caution is, AB linear amps are only on average about 33 percent efficiency. So, obviously if you are using AM the pep will be 4 x carrier. The linear needs have balls to do 4 x carrier without becoming flat toped out.
The little rig I have FMs is useless really without a DDS, and could in principle be used to drive a linear to a practical, maybe 100-200 watts. :P
Perhaps some voltage regulation on the oscillator stage would reduce the FMing?
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It's regulated, obviously!
Digiplod can build his own!
Str.
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When I noticed some FM on the Radio Systems, I Am Radio (a.k.a. updated Talking House), TX, I grounded the case of the main crystal to chassis ground and that reduced the FM to better than 1/2 of what it was. The 13.560MHz AM Pixie-like TX I have, the main crystal is 13.560MHz (Thank you Fearless Fred on that one!). That crystal is also tied to chassis ground. On FM listening, I really have to crank the volume all the way to just hear it. It's better than any commercial AM TX gear that I have. You might want to give that I try. Where did I get the idea from? Before ICF (International Crystal Manufacturer.), closed up, I asked their engineers if that was a good practice to ground crystal cases, and they recommend that indeed.
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It's grounded already. I've already explained the fming is due to an inductor used to pull the Xtal L.F.
All future LuLus will use an AD9833, hopefully immune from any fming issues.
The end!
😉
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Just add a final (final!) note on the fming issue.
I have invested in an 8902A and can measure the fming, distortion, power, Freq and +/- mod level.
The fming issue is only present at mod levels exceeding 100%.
The mod level on the Tx is set by a control on the front panel. This does NOT adj the power and WILL cause distortion, fming of the carrier and causing the mod amp to cut out as it has a built in DC detectior to protect itself, if it is set too high.
The ONLY real way to monitor this with a scope initially and making sure ALL audio material NEVER exceeds a level that causes the mod level to exceed 100%.
To make sure your audio is LOUD it will need to be compressed. We're NOT talking MP3 compression here but 'audio compression' which raises the average level so everything is LOUD! Simple to achieve with pre recorded material as there's a wealth of software out there. However if you're running live you will need a decent audio compressor/limiter. I'm not going to go on about which one is best but you can spend $1000's on a real good one! However doing this with software on prerecorded material costs nothing!
If you'd like any more info please PM me.....
Str.
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These Re fine transmitters and Stretchy is the man!!