Does anyone know the rules for part 15 broadcasting on the shortwave band?
It seems like it's been so quite on the forum the last couple days..
Nounoson, here's a link to a previous thread to answer your question: http://www.part15.us/index.php?q=node/2065
Hello Group! I'm back after a year's absence! (No excuse...my interest in Pt. 15 SW has just been drifting up and down...right now it's way up there again, especially after reading the success stories of a couple of you guys finally getting modulated carriers on the air on 13.560!
For those like me, EXTREMELY challenged in transmitter contruction, has anyone considered severly attenuating an old, already built, AM ham transmitter? The following example is EXTREME overkill in the power dept., but with enough attenuation, you could be on the air in minutes after obtaining the transmitter.
When I was a kid, (15 in '67) I had a pirate station on the AM broadcast band. (1610khz) My transmitter was a Globe Scout 65A, vintage 1955. What a beautiful sounding rig! This thing was PLATE MODULATED, with an almost perfectly flat EQ curve, no highs or lows roll-off, and you could sure appreciate that when our music came thru sounding every bit as good as the commercial stations. (As least WE thought so....) The Globe Scouts also featured a very broad tuning overlap in the oscillator, driver and final circuits, enabling me to simply pop in a xtal for 1610khz, switch it to the 160 meter band, tune it up and GO! NO modifications necessary whatsoever! It wouldn't surprise me in the least to be able to do the same thing on 13.560 with the bandswitch set for 20 meters.
Biggest problem is, this is a 50 watt xmtr! Would the solution be to try and modulate the oscillator or the driver and use that? Or, should one utilize that beautiful plate modulation by using the final's output, if it could be attenuated enough.
Could this be as simple as loading the output into a "Cantenna" dummy load? Or would even that allow too much radiation to be legal?
What do you think, guys? The nostalgia of using an old Globe Scout 65A for my station again is almost too much to hold back! And the time and trouble saved by having a pre-built, proven transmitter...Priceless! (To me, anyway.) These things come up on e-bay every few weeks. Should I go for it? Ron Kocher - Palm Coast, FL back again!
Can you hack the circuit to pull the signal out before the final? you might find a pre-output stage that puts out a manageable power level.
If not, you could use a signal divider and broadcast from the (very) weak side side and put a dummy load on the strong side.
Check pages 44 - 46 of this file for more info
Thanks for the link to the power dividers - that might be the way to go.
Yes, I could hack into an earlier stage, but the ouput would just be a straight carrier. I would have to modify the modulation section also to modulate an earlier stage. Modulation in the Globe Scout 65A takes place by plate modulating the final stage only. And it's such good, high-fidelity modulation! (Unheard of in the newer rigs...after the 50s went by, hams became concerned more with "talk power", "punching through" and "readability", so bandwidths were tightened up, Lows and highs were rolled off and fidelity took a back seat.)
Also, leaving the rig stock is easy and quick. But, there's way too much power.
Whenever I've used a dummy load, the signal is never kept completely from radiating. There's always some that gets out. I was thinking of loading the Globe Scout's output into a dummy load, and using that as my antenna. I figure if I can restrict it so it can't be heard any further than the distance you guys are getting with about 2 milliwatts into a dipole, I would be in the ballpark. (At least until I get get it officially measured in uv/m)
My next test will be to load about 50 watts from the 20 meter rig I already have into a dummy load and see how far I can hear it. That way I should have an idea if this will possibly work before I buy the Globe Scout. I'll keep you all posted! Ron Kocher - Palm Coast, FL