Talking House AM Transmitter Questions

[AMRadioGuy]

I recently purchased a TH5 off of eBay, primarily to put audio from my CBS Audimax/Volumax on the AM airwaves to tune in on vintage transistor radios.

The transmitter did not come with the original antenna, unfortunately. This means I need to make one on my own. I connected a relatively short length of common speaker wire to the antenna post on the back of the rig and while I was able to pick the signal up on a radio, it had a large amount of hum. Just for kicks, I tried disconnecting the antenna wire and the hum largely went away. My question is this: can I run this transmitter without an antenna connected to it (I believe usually the answer would be "no" but this has an ATU built in so I'm wondering if that changes things). That seems to help kill the awful hum I'm getting with the antenna attached.
I'm also wondering what antenna setups I might be able to make for the TH5 easily and cheaply that would yield decent results.

Oh, and of course, I'm looking to keep this TH5 legal. I'm not looking for advice on how to "hotrod" the transmitter to boost the power/range beyond legal limits. Lets please keep this thread within the confines of Part 15!

Thanks!

 

[KeithE4]

100 mW DC input to the final amp (50-75 mW RF out, depending on the amp device's efficiency) into a 3 meter antenna is what's allowed. That's good for 100-200 feet and keeps it legal. But the ERP is in the microwatts at best, since a 3 meter antenna is less than 1% efficient, especially if there is no radial field under it (which is of questionable legality, even though it doesn't radiate).

 

[AlligatorClipz]

If your talking house came with the factory wall wart with the ground pin on it, try plugging it into one of those ground adapters so it doesnt have ground pin connected. I have a TH5 and it humms like no tomorrow, but it doesn't know the words. Also, the AGC and filtering in the audio input don't do the unit any favors. Even with the factory wire, the signal is dead as soon as I pull out of the driveway.

 

[CentralFL]

Is there a reason you want a talking house AM? There are plenty of legal FM micropower transmitters available.

I have one from CCrane and it works great to stream stuff around the house.

 

[cc333]

If you have a spare $800-$1,000 – who does anymore? – a ChezRadio ProCaster or Hamilton AM1000 Range Master would be far, far superior to a Talking House in almost every way imaginable.

Plus you can enjoy a legal range of up to a mile or more, depending on well you mount the transmitter.

FM micropower transmitters are nice, but the legal limits are much more strict, so the useful range is basically limited to a few dozen feet.

c

 

[Mediafrog+]

If you have a spare $800-$1,000 – who does anymore? – a ChezRadio ProCaster or Hamilton AM1000 Range Master would be far, far superior to a Talking House in almost every way imaginable.

Many years ago there were a lot of cheap Part 15 AM transmitters and modulators available, often in kit form. Those seem to have disappeared. Anyone know if they still exist anywhere? Part 15 FM units are fairly easy to find.

 

[CentralFL]

If you have a spare $800-$1,000 – who does anymore? – a ChezRadio ProCaster or Hamilton AM1000 Range Master would be far, far superior to a Talking House in almost every way imaginable.

Plus you can enjoy a legal range of up to a mile or more, depending on well you mount the transmitter.

FM micropower transmitters are nice, but the legal limits are much more strict, so the useful range is basically limited to a few dozen feet.

c

The CCrane one definitely goes a bit further. There may be a video or 2 on youtube showing how to improve its signal. But nothing to get you in trouble....maybe 300 feet. Until that lottery money comes in, it will cover most people's house and garden. ;-)

 

[Mediafrog+]

The CCrane one definitely goes a bit further. There may be a video or 2 on youtube showing how to improve its signal. But nothing to get you in trouble....maybe 300 feet. Until that lottery money comes in, it will cover most people's house and garden. ;-)

I’ve long been curious how far one of those Part 15 FM units would go if it was at a high elevation and you used a sensitive receiver with a large yagi antenna pointed right at the transmitter location. I suspect you might get a detectable signal up to two miles away if there was no terrain or building blockage.

 

[kevtronics]

I’ve long been curious how far one of those Part 15 FM units would go if it was at a high elevation and you used a sensitive receiver with a large yagi antenna pointed right at the transmitter location. I suspect you might get a detectable signal up to two miles away if there was no terrain or building blockage.

I get about that far with a Whole House FM Transmitter 3.0, from hilltop to hilltop. And no, I'm not using the secret "high power" mode.

 

[yeoldeschool]

I get about that far with a Whole House FM Transmitter 3.0, from hilltop to hilltop. And no, I'm not using the secret "high power" mode.

How is the linearity of that unit? Can you deliver highly processed audio with tightly controlled peaks to it, and see the same tight peaking "in the air" with something like a modulation monitor or an MPX recorder?

 

[kevtronics]

How is the linearity of that unit? Can you deliver highly processed audio with tightly controlled peaks to it, and see the same tight peaking "in the air" with something like a modulation monitor or an MPX recorder?

The Whole House transmitter has a built-in 15 kHz filter to protect the pilot, but unlike the C.Crane transmitter which has a rather aggressive audio limiter, it will let you overmodulate, so it's good to put some processing ahead of it. I'm playing Smooth Jazz through it, so I'm not so concerned about being the loudest on the dial.

One big annoyance with the C.Crane transmitter is that it has a "soft" power button, so if it loses power, it won't come back on when you reapply power -- you need to press the power button again.