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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 5:57 pm 
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Flinx wrote:
power the unit with a ground pin not connected to ground.

ground the TH case run the antenna in the same plane as the ground plane 1/2 the distance of the antenna length to ground. then turn on the unit.

that's what I did.

Got a couple questions - what did you ground the TH case to? When you say ground plane, did you make one out of something and how large? How far below the TH is the ground plane?
Thanks!

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 6:12 pm 
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In my case it was a large metal desk.

then I ran the antenna parallel to the desk.

length of wire was random maybe 5 or 6 feet long.

whatever you do with the antenna the unit needs to be power cycled and the antenna retuned each time for testing.

You could use a pipe or possibly actual ground, I never tried that.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 6:22 pm 
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maybe later today (after I finish making cookies) I will try and replicate my results and video it.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 7:11 pm 
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cookies are made, video has been shot, let me edit and post to youtube.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 7:28 pm 
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New video is rendering, here is the old video if you are interested.
https://youtu.be/l7ZHQvikSQM

New video will be available in about 45 minutes.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 7:58 pm 
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Ok, here is the new video, I recommend watching the old one as well.
https://youtu.be/6Jm06SE9P8g

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 8:22 pm 
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A couple more observations – this is with things setup as described in my last update where I wasn’t getting any hum running the TH on a 12V battery downstairs in my rec room.

Next I disconnected the battery and plugged the 18V power supply into a wall outlet. This was with a 2 to 3 wire adapter, so the TH was ungrounded. Now I was getting a slight amount of hum but not enough to call it a problem. In this case, it didn’t matter how I oriented the Sony portable. The slight hum was always there. That was with the mp3 player on pause. I couldn’t detect any hum with music playing.

Next I removed the 2 to 3 wire adapter. Now the TH was grounded to the house wiring. I couldn’t detect any change from the previous test. This room is a very quiet room as far as AC noise. Nothing was plugged in except the TH.

These tests seem to suggest the TH is going to work ok (maybe I should say good enough) if it is in an AC quiet room no matter how it is grounded or powered.

Next I held the Sony up against the antenna wire. In other words, its ferrite rod was as close as possible to the transmitting antenna. Wouldn’t you think that would be worst case for picking up hum? There was nothing. That was with it powered by the 18V power supply.

Then I started moving the Sony around the outside of the TH case. Whoa… there are several places where hum/noise skyrockets. That was also running on the 18V transformer. So, I tried the same thing while powering it with my 12V battery. Dead silence – no hum/noise around the TH case. Does this mean anything? It’s sure is suspicious!

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Mon 23, 2019 8:41 pm 
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Flinx wrote:
Ok, here is the new video, I recommend watching the old one as well.
https://youtu.be/6Jm06SE9P8g

Hey, thanks! I just watched both of your videos and picked up some tips. I did try improvising a ground plane below the antenna, but I wasn't getting any hum in my rec room before, so I couldn't really tell a difference.

Normally I have my TH in my wife's music room, where there is some AC noise. I do get hum there, but I can orient her Sony portable radio and eliminate it. The main reason I'm still experimenting with the TH is I wanted to be able to pick it up on my old tube radios for testing purposes. I can't eliminate the hum on them. I have to run them on an outside long wire antenna which picks up the TH hum like crazy - that's with the TH in her music room.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 2:15 am 
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Marvin, with the TH in your quiet room, and the radio elsewhere in the house, do you hear hum? I'm trying to understand why some people have issues with the AC re-radiating the signal (plus hum), and some do not. Just about everyone has AC wiring in their homes. How far from AC wiring does the TH need to be, I wonder? Some homes have metal conduit. That might be helping.

I also wonder if the antenna length could be adjusted to reduce its ability to Tx onto the wires? Horizontal orientation should be better. An antenna "ground plane/return" (counterpoise) might help get out more signal, but I can't see how that would help to keep the signal off the AC lines. Maybe it has to do with the size of the effective radiating loop.

You and I have clearly shown with our experiments, that the majority of the hum (we at least) are hearing is coming from the carrier getting onto AC lines, not from the TH itself. (Powering with battery, zero ground reference, hum goes away when power removed, etc.)

I cannot think of any way around this, for any transmitter. Maybe lower the power. Maybe shorter antenna. If the AC lines are exposed like Romex is, i.e. not run through metal conduit that can be grounded, I don't see any way around it. But I will say that at some point, the distance TO the AC wires will be large enough to drop the AC line pickup a lot because of the inverse square law. And then it's just up to the radio receiver to be able to pick up the TH signal.

Edit: And I live in a modest house, with small rooms. In any room, except maybe the family room (which has more electronic noise), I'm within 5-6 feet of AC wiring.


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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 5:02 am 
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After reading the above post, I turned on my SSTrans 3000, located in my den, and then went into the kitchen and turned on my Motorola Ranger 700 four tube radio.

Distance between receiver and transmitter, about 70 feet. House wiring, Romex. Transmitter antenna length, about 6 feet, oriented vertically. Grounded to an AC wall plate keeper screw.

I did not immediately turn on a music source, and noticed a slight hum from the transmitter, on the receiver. Once the source (Grace internet radio) was turned on, the music totally concealed the hum, to where it was not audible.

I would suggest that the Talking House is simply not designed for our purposes, whereas the SSTrans is, esp with a stereo input and adjustable modulation/gain/compression controls.

The gain on mine is set at 3/4 rotation, compression and modulation at about 1/2. These settings are important in order to get the best quality signal, and I don't remember the Talking House 5 that I previously had, as having any of them.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 1:33 pm 
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fifties wrote:
I did not immediately turn on a music source, and noticed a slight hum from the transmitter, on the receiver. Once the source (Grace internet radio) was turned on, the music totally concealed the hum, to where it was not audible.

I would suggest that the Talking House is simply not designed for our purposes, whereas the SSTrans is, esp with a stereo input and adjustable modulation/gain/compression controls.

The gain on mine is set at 3/4 rotation, compression and modulation at about 1/2. These settings are important in order to get the best quality signal, and I don't remember the Talking House 5 that I previously had, as having any of them.

I know better than to argue with results, and I don't challenge yours. But TH is a supporter of this site, and certainly DOES advertise that the TH is designed for our purposes. I bought one partly because of that advertisement. "broadcast to your classic receiver with a classic trasmitter." It's right there on the page as I'm writing this.

I design printed circuit boards for high speed data communications equipment. We frequently have 20-28 layer boards. The equipment costs a mint, but it needs to perform perfectly, and it's designed with Quality as #1. As an experienced designer (though much more digital than analog), my opinion is that the TH was not designed with quality in mind. Even so, if pinching pennies, I would have put that circuit into a minimum 2-layer PCB, so that I could control the shapes of the power and ground planes. It would add very little cost but almost certainly offer improved performance.

That is why I initially thought the hum was because of their circuit design and layout. But, if you remove all ground and 60Hz references from the unit, as we did, one has to wonder: what is the mechanism for the hum? That is where the AC line re-transmitting theory comes from. I didn't make that up; I read it from others. As I said before, I do not completely understand that mechanism. But if that's all there is to it, no transmitters would work (at least in my house). I guess that is what I need to find out next. I will build the LM386 design and try it out.

As for the TH, I'm done with it. I don't have any more time to waste on it. It may or may not have to do with some aspect of their design, but it does not perform with any level of acceptablility, in my house, and it really is far more complicated than necessary (for me), simply because of what they needed to do to accommdate all the options and the frequency agility.

You know, they are also not out of business. I doubt most people have the same hum experience I have had, or the business would fail, right? There has to be more to this picture, that I'm just not seeing.


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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 2:00 pm 
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My 1970 house is a "raised ranch". The garage and rec room are on the bottom level and are open to the street. All else is on the 2nd level, which is walk-out to the back yard. We only have 100 amp service. All the wiring is romex, no conduit. All of the outlets have a ground. My neighbor and I share a street-side transformer. We are the only ones on the 250' run from the highway's 13.8KV line. It's impossible to get more than 6-8' from any power lines in the walls or floor on the living level. I can get maybe 10' from power lines in the downstairs rec room, and it has no power lines in the concrete floor. I wonder if anyone else is as close as I am to main highway 13.8KV power lines?

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 4:25 pm 
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I have been following this thread and sometimes I see something that is confusing.
fifties wrote:
whereas the SSTrans is, esp with a stereo input

I didn't know AM supported stereo on these transmitters ?

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 6:26 pm 
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[quote="pauls.ironhorse"
I didn't know AM supported stereo on these transmitters ?[/quote]
.
...The SStrans has stereo inputs, but they just combine the stereo input into mono. So, the audio is definitely only mono.


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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 7:22 pm 
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On occasion I have a hum on my several homebrew transmitters both tube and SS.
I took down a CB antenna and left the 50' coax laying on the ground. Connecting the center pin to any of my transmitters gives me a 99% clean sound heard for house or two. :shock:
I get a good signal using a ground rod as the antenna also.


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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 8:09 pm 
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DaveInNC wrote:
fifties wrote:
I would suggest that the Talking House is simply not designed for our purposes, whereas the SSTrans is, esp with a stereo input and adjustable modulation/gain/compression controls.

I know better than to argue with results, and I don't challenge yours. But TH is a supporter of this site, and certainly DOES advertise that the TH is designed for our purposes. I bought one partly because of that advertisement. "broadcast to your classic receiver with a classic trasmitter." It's right there on the page as I'm writing this.

my opinion is that the TH was not designed with quality in mind.


You know, they are also not out of business. I doubt most people have the same hum experience I have had, or the business would fail, right? There has to be more to this picture, that I'm just not seeing.

I just looked over their ad, and see no mention of what you posted AFA "broadcasting to your classic receiver".

Regardless, their unit was designed for advertising houses for sale to passing cars, and apparently that aspect is a viable enterprise, whereas for our purposes, it's not. Your own findings AFA reception quality and PCB design seem to water down any claim they make.

There are several factors regarding the quality of AM transmission. Weather, for one, both humidity and temperature, placement of the antenna, the type of grounding used, the power supply interaction, and of course circuit design.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 8:34 pm 
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fifties wrote:
DaveInNC wrote:
fifties wrote:
I would suggest that the Talking House is simply not designed for our purposes, whereas the SSTrans is, esp with a stereo input and adjustable modulation/gain/compression controls.

I know better than to argue with results, and I don't challenge yours. But TH is a supporter of this site, and certainly DOES advertise that the TH is designed for our purposes. I bought one partly because of that advertisement. "broadcast to your classic receiver with a classic trasmitter." It's right there on the page as I'm writing this.

my opinion is that the TH was not designed with quality in mind.


You know, they are also not out of business. I doubt most people have the same hum experience I have had, or the business would fail, right? There has to be more to this picture, that I'm just not seeing.

I just looked over their ad, and see no mention of what you posted AFA "broadcasting to your classic receiver"

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 10:24 pm 
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DaveInNC wrote:
That is why I initially thought the hum was because of their circuit design and layout.


In my limited experience building circuitry on perfboard, it is indeed most likely their circuit layout that maybe makes them more prone to hum than others.

DaveInNC wrote:
But, if you remove all ground and 60Hz references from the unit, as we did, one has to wonder: what is the mechanism for the hum? That is where the AC line re-transmitting theory comes from. I didn't make that up; I read it from others. As I said before, I do not completely understand that mechanism. But if that's all there is to it, no transmitters would work (at least in my house). I guess that is what I need to find out next. I will build the LM386 design and try it out.


I wouldn't mind getting one and trying to isolate the audio input using a transformer and seeing if that eliminates the hum or reduces it.

I do know with my two tube transmitter, just doing that solved most of the hum issues I had.


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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Tue 24, 2019 10:34 pm 
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DaveInNC wrote:
fifties wrote:
DaveInNC wrote:
I know better than to argue with results, and I don't challenge yours. But TH is a supporter of this site, and certainly DOES advertise that the TH is designed for our purposes. I bought one partly because of that advertisement. "broadcast to your classic receiver with a classic trasmitter." It's right there on the page as I'm writing this.

my opinion is that the TH was not designed with quality in mind.


You know, they are also not out of business. I doubt most people have the same hum experience I have had, or the business would fail, right? There has to be more to this picture, that I'm just not seeing.

I just looked over their ad, and see no mention of what you posted AFA "broadcasting to your classic receiver"


Image

OK, I went into their ad and didn't see any mention of it. Yes, no argument that it will work, it just won't work to anywhere near perfection for music, but maybe for OTR it's delivery is acceptable.

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 Post subject: Re: Talking House AM Transmitter MODIFICATION IDEAS HELP?
PostPosted: Dec Wed 25, 2019 1:23 am 
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fifties wrote:
Yes, no argument that it will work, it just won't work to anywhere near perfection for music, but maybe for OTR it's delivery is acceptable.

Agree...still, some people have good luck with it... Someone like Binh could probably reverse engineer the circuit enough to figure out what needed to be done to make it better--indeed, already has, partly. LT Spice sims even. But I'm not sure improvements could all be put into practice just by changing the existing components and modifying traces. Maybe, but it's probably beyond my analog skills.

Also, it's not a "quest" for me to get the TH working in my house. I just wanted to play some stuff through my radios, and I didn't pay that much for it to have to keep it. I have enough projects, like the new toys I got on CL this past week (a non-working Sencore LC53 for one--now there's a tough nut to crack.) Anyway, I want to build one of the other little transmitters you guys did here a while back. LM386, 6888, etc. Just for grins. They'll probably hum for me as well.


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