i’ve seen little 6mhz kits, thought about sending music to a nearby radio seeing how it sounds, I suppose it would not be possible for afew watts music transmission to reach another country? it requires the messy earth, spiders web of aerials in the back garden, burying bins, you get from top cat, I suppose unlikely to reach any bass bins. It would be funny to hear abit of heart Amanda Holden coming across, just seeing how things sound.. I suspect other than seeing how different music sounds its abit of a dead end, best sticking over fm I suppose, even with crappy chips or without pre emp it does sound better, keeping fm alive with the sound of music

I thought fm transmitters were rare, then I looked for a shortwave transmitter, kind of like looking for a copy of fly fishing by jr heartly The other thing i'm wondering is there a particular time when they transmit, with medium wave there is the skywave at night, abit like throwing salt over the shoulder, maybe a mystery Do stations on shortwave switch on at a particular time to reach a particular country, are they there through out the day, not saying i'd want a big bulky shortwave transmitter as I don't have a ship to put it on, just curious about it.

I believe Mike currently runs a 400W solid state PWM rig, this is fairly typical of the current crop of low power AM shortwave pirates. Most seem to run power somewhere in the low hundreds of Watts (carrier, peak will be 4 times that for AM) but you do get some running kilowatts. Rigs are easily built and available for sale from various places.

Most shortwave reception is via the ionosphere - even running a couple of hundred Watts on 49m, for example, won't go far on the ground. In theory, you can reach the ionosphere with a few Watts but reception at the other end will be fleeting, which is part of the fun for some listeners (not my idea of fun to be honest). There are low power HF beacons in the USA getting reports from far afield, some running a couple of Watts and also things like the WSPR programme which runs low power digital modes to analyse HF propagation.

I've got a 50W (carrier) HF rig here that I built a few years back. It's no bigger than your common or garden pirate FM 300W rig but it's oversized, to be honest - lots of empty space in the box and heatsink way bigger than required. It's possible to build a higher power HF box which is smaller than that - using a class D/E RF stage and PWM modulator. No inefficient linear RF or modulator stages, so no massive heatsinks and no bulky modulation transformers either. Additionally, modern ferrite materials mean smaller chokes/transformers of a given spec are possible without the cores saturating.

The HF bands' propagation characteristics all vary differently with daylight hours, time of year and other factors. It's quite interesting! There used to be a few Euro pirates audible after dark on 75m (haven't listened for a while) but there are plenty on 49m usually audible on Sunday mornings. There are loads of HF pirate logging sites around so you can get some idea.

As regards antennas for HF, it's a different animal than MW. Dipoles are more easily constructed due to the shorter wavelengths as well as a variety of other antennas. Inverted L is also popular but there are many more. No dustbins required.

I have had letters from other side of Europe running just 5W carrier and simple dipole.

Many smaller stations use just radioamateur rigs as transmitter, some folks have old R&S boatanchors.

One station that I know rocks two BLF188X boards from China, about 500W carrier out.

Johnny Tobacco / Radio Abu Dhabi runs "all of it, plus some extra", and you can see it, he has wide spectrum.

Some old eastern block stations run huge powers, cold war era tubes and gear is cheap there.


I have been looking old R&S SK010, not to use but as museum piece in my shop.

I watched a video not so long ago were someone was using the harmonic of a transmitter they were listening some distance away on an sdr, it was just a beacon or something, don’t know what aerial they were using, suspect the power was very low on it, some kind of ham I think. They may of even tuned to the antenna to the harmonic frequency.

I saw some were that offshore stations would use shortwave, aswell as medium wave the stalt water would help the transmission, maybe more at medium wave, suppose its mostly why I was thinking of them as been big bulky. Obviously something does afew watts would be not so bulky, I suppose any transmitter is likely to be big if its doing 100watts, I don’t think thought i’d want to using one of those.

It does seem to me that some old radios used shortwave too, maybe those old war time ones but i’m not sure, thats maybe why there are kits, 6mhz or 21mhz. I kind of suspect they might be used for relaying old wartime speeches through radios. I guess they maybe just use a crystal to do this, problably no market for shortwave rigs.
I’ve played about with crystal oscilators, listened to them on band II, there full of harmonics, ok for sending a signal a very short distance, the lack of mod is good enough for am. I don’t know if you could get wideband mod with an op amp, I suppose you’d still have the signals on 88,96, aswell as 108 that makes them unsuitable, they are the simplest way of generating a stable transmission.
It did suprize me there was no tuneable rig for sw, suppose there might be an rf generator, if someone wanted to tune to different channels over shortwave, if they wanted such a thing. Suppose the fact those 6/21mhz kits can only go a short distance the frequency is not that important so a tuneable rig is not important. the war time speeches go ahead

Seems to me I was right that afew watts wouldn’t do anything, if it wouldn’t be audiable on an sdr to others? I don’t think there would be much point, seems to me the only other thing would be walking around a mile away trying to hear something of this nature, suspect it would be only done once, not sure people would want to hear carly rae jessen coming over shortwave. You would then have to have a radio with a telescopic anntenna, medium wave uses the ferrite rod, fm the headphones wire, the quailty been less to fm.

I think I've seen those small 6MHz transmitters on eBay - crystal or VFO controlled, either series modulated with a linear amp through a small choke or using a modulation transformer. Probably only intended to broadcast your wartime speeches across the room but look as if they should sound good on your old valve set.

radionortheast wrote: ↑Fri Aug 08, 2025 10:18 am I suppose any transmitter is likely to be big if its doing 100watts, I don’t think thought i’d want to using one of those.

For the actual transmitter part, not true for the reasons I outlined above! I'm sure Mr. Stretch will be glad to further debunk this myth. Your power supply and any ATU or balun (not always needed) would add size, but not too much.

As regards "tunable" rigs for SW, not sure what you mean. It's harder to do "broadband" on HF for a number of reasons especially with class E which requires careful tuning to make it happen - you'd build with a specific frequency, or (small) range of frequencies in mind. Another big one is filtering if you need a multi-band TX - at lower frequencies you want your LPF to roll off in the HF band where you may also want to transmit at other times. So, many HAM rigs have switched filters. If you're building for broadcast radio though, not a problem unless you want to run the same rig on different bands at different times of day say, moving from 75m to 31m or something. For the actual signal generation part, a programmable DDS module will generate any frequency up to VHF (and probably beyond) for a few quid. It's the stages after that where it gets a bit trickier!

radionortheast wrote: ↑Fri Aug 08, 2025 10:18 am they are the simplest way of generating a stable transmission.

Not if you want to FM it (for example).

radionortheast wrote: ↑Fri Aug 08, 2025 10:18 am Seems to me I was right that afew watts wouldn’t do anything, if it wouldn’t be audiable on an sdr to others?

Down the road you'll be fine but further than that and your mileage will vary, as they say. It's similar, but not technically the same, as the argument about "30W on FM will go 15 miles". Yes on HF it might go hundreds of miles under the right conditions, but will it be listenable for more than a few seconds at a time?

HF ham radio which is 'opened up', that's a 1 min soldering job, put MP3 player speaker to microphone with an elastic band round, run 20W of the 100W into a vertical. SW sounds diabolic anyway so it will make no difference. Other than the 12M vertical antenna probably the easiest band to get on I would have thought.Nothing to it, super clean second hand ham rigs already exist.

Can you be bothered though. You'll never know who heard you without a load of other hassle. Relax and listen instead, better.