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PostPosted: Nov Fri 19, 2010 3:55 am 
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Joined: Feb Wed 06, 2008 5:17 am
Posts: 762
Location: Ferdinand, IN
Ha ha, yeah, whatever.

I didn't mention that when I first tried it out of the box, it was set to a frequency on the high end of the band - and hummed.

Don't think I haven't thought about reselling the thing on eBay. But that would not be ethical unless I sold it "as-is, where-is" and disclosed the humming.

How bad? If it is being modulated with strong audio, it is almost unnoticeable. But once a song reaches the end or otherwise gets quiet, then you can really notice the hum.

I quit messing with it after going through the list I posted above; it was too annoying. I might use it during Christmas and just put up with the hum, as I would like to play 1940s-50s era Christmas music through the old radios in the house this season.

I set mine to the lower end of the AM band since all of the local and regional AM stations in my area are on the high end of the band.


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PostPosted: Nov Fri 19, 2010 4:11 am 
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Joined: Jan Sun 04, 2009 6:43 pm
Posts: 1577
It sounds like you just have a defective unit. I have owned/currently own several TH transmitters, various model numbers (4.0, 4.6, 5.0). None have had hum that couldn't be fixed with a Radio Shack isolation transformer. Most had no hum at all.

This has always been a problem with TH - unit to unit quality control. There are bad ones and there are good ones.

"Are you a good witch, or a bad witch?" :lol:


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PostPosted: Nov Fri 19, 2010 4:16 pm 
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Joined: Jul Wed 22, 2009 8:32 am
Posts: 3805
Ron Ramirez wrote:
I set mine to the lower end of the AM band since all of the local and regional AM stations in my area are on the high end of the band.

Ron I don't mean to aggravate you. I can tell you are frustrated and I agree, TH units vary and the 4.6 is one of the older ones. I am not trying to tell you what stations you have, but I looked up Ferdinand, IN and you have lots of room above 1580 Khz. I went to radio locator. That area only has two strong'ish stations, 990 and 1160 Khz. There is nothing above 1580 Khz (local+distant+fringe) according to Radio-Locator.

Try 1590, 1600 or 1610, which will still work with old radios. I found even if there is a weak signal the TH has the power to over ride it. At night these sould be fine. 1230-1490 Khz and above 1570 Khz, has few or no Clear Channel 50 KW night time stations.

Antenna - I fixed my hum again but it took stretching the antenna out horizontal. The ground wire out the door into the dirt helps most of the time. Cheers

_________________
Tube: AM/FM Zeniths, RCA, TrueTone table tops; Transistor: Kaito KA1103, TenTec RX320D, Pioneer SX780


Last edited by gmcjetpilot on Nov Fri 19, 2010 4:23 pm, edited 1 time in total.

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PostPosted: Nov Fri 19, 2010 4:20 pm 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Naddy69 wrote:
It sounds like you just have a defective unit. I have owned/currently own several TH transmitters, various model numbers (4.0, 4.6, 5.0). None have had hum that couldn't be fixed with a Radio Shack isolation transformer. Most had no hum at all.

This has always been a problem with TH - unit to unit quality control. There are bad ones and there are good ones.

"Are you a good witch, or a bad witch?" :lol:


Which radio shack isolation transformer are you refering to? I'm willing to try anytihng at this point.

Ed

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 Post subject:
PostPosted: Nov Fri 19, 2010 4:32 pm 
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Posts: 3805
ecarfar wrote:
Which radio shack isolation transformer are you refering to? I'm willing to try anytihng at this point. Ed

Image
Ground Loop Isolator Model: 270-054 | Catalog #: 270-054
http://www.radioshack.com/product/index ... Id=2062214

It has 88 reviews and 4.5 out of 5 stars, so that is a good sign. However this is just a transformer and may be a filter cap. Radio shack use to sell a do it yourself kit version, just parts for a few bucks. I think if you hunt you will find this in other brands and quality. If your TH is hum'in with nothing plugged in or with the outgoing message, I doubt this will help, but it's worth a try. If it is in the store you can try it and bring it back. This is for stereo and the RCA plugs is a little inconvenient, needing adaptor.

You will find this link interesting
http://www.epanorama.net/circuits/audio_isolator.html

I thing the TH and audio sources suffer from IMPEDANCE matching issues, so matching transformers help. The link above talks about how high quality mini audio transformers are expensive, however since this is AM radio that might not be a big deal. You might try one of radio shacks cheap isolation transformers.
http://www.radioshack.com/product/index ... Id=2103994
http://www.radioshack.com/product/index ... Id=2103254

This link shows how to use it.... and the specs
http://home.comcast.net/~wuhu_software/EliminateHum/

An iPod is about 32-42 ohm impedance for the phono or "earbud" output. Not sure what the TH input impedance is, but if it's 8 ohms the audio transformer will help, but that does not usually cause hum. Worse is trying to connect BALANCED audio output (where neither side is ground) and UNBALANCED (where one side is hot, one ground) audio. The solution for that's a transformer, or just use half of the balanced output, eg just connect one side to hot, no ground.

I found a good way to isolate (eliminate ground loop) and match is to do it with solid state electronics. There are these little "CMOY" amps. It is named after the guy who popularized this project of making little battery powered amps for boosting weak audio output from portable audio devices to drive full headphones or amps needed a full line-in voltage. All parts are common off the shelf. It's just a stereo op-amp IC stuffed into a little box (typically an "Altoids" tin). You add capacitors, pot, on-off switch, jacks in/out, and you're good to go. Not only does it isolate it amplifies, taking a low line level and making it a higher phone output. These are also called headphone Amps. They are NOT made to drive speakers. I find the caps and IC amp isolate the input and output. If you google CMOY you will find a ton of info.

I found my PC audio out gave some of the best sound, which is not always the case.

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Tube: AM/FM Zeniths, RCA, TrueTone table tops; Transistor: Kaito KA1103, TenTec RX320D, Pioneer SX780


Last edited by gmcjetpilot on Nov Fri 19, 2010 5:05 pm, edited 2 times in total.

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PostPosted: Nov Fri 19, 2010 4:57 pm 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Wow, thanks for all that! But it's not going to help me at all. My TH produces the hum without even the audio connected. All I have to do is plug it in and every radio in the house has that annoying hum in and around the frequency on the TH.

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Last edited by ecarfar on Nov Mon 22, 2010 4:17 pm, edited 1 time in total.

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PostPosted: Nov Fri 19, 2010 5:17 pm 
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ecarfar wrote:
Wow, thanks for all that! But it's not going to help me at all. My TH produces the hum without even the audio connected. All I have to do is plug it in and every radio in the house has that annoying hum in and around the frequency on the TH.

Yea I went through this before with other applications. Also going from stereo to mono is a pain. You can get two of those audio amps to mix left and right into one.

Image

The other mix circuit stereo to mono is either to resistors or two resistors and capacitors. You never want to tie the left and right together direct, even an iPod. There is some isolation going on here as well.

Image


Here is my portable headphone amp
Image

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Tube: AM/FM Zeniths, RCA, TrueTone table tops; Transistor: Kaito KA1103, TenTec RX320D, Pioneer SX780


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 Post subject:
PostPosted: Nov Fri 19, 2010 7:22 pm 
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Joined: Feb Wed 06, 2008 5:17 am
Posts: 762
Location: Ferdinand, IN
gmcjetpilot wrote:
Ron I don't mean to aggravate you. I can tell you are frustrated and I agree, TH units vary and the 4.6 is one of the older ones. I am not trying to tell you what stations you have, but I looked up Ferdinand, IN and you have lots of room above 1580 Khz. I went to radio locator. That area only has two strong'ish stations, 990 and 1160 Khz. There is nothing above 1580 Khz (local+distant+fringe) according to Radio-Locator.

Try 1590, 1600 or 1610, which will still work with old radios.

No worries GMC, no offense taken. :)

Older radios such as the Philco 70, 90 and 112 only tune as high as 1510-1520 kc so I wanted to transmit on a lower frequency so that all of my old radios could receive the signal, not just sets made after 1931.

I used Radio Locator to search for AM signals in my area. I chose to include fringe stations. I can pick up most if not all of these on my better Philcos such as the 116B, 16B and 18B. There were no stations in my area (including fringe stations) operating on 660 kc, so that is why I chose that frequency. That plus the fact that older receivers cannot receive stations much above 1510 kc.

When I pulled the TH out of the box and tried it the first time, the antenna was lying on the floor. When I moved it to another room and set it up, I taped the antenna vertically against the wall.

I'll try positioning the antenna horizontally again, and will try a 3 prong to 2 prong adapter, before giving up entirely (hoping Ed finds a solution that I can apply to my TH).


Last edited by Ron Ramirez on Nov Fri 19, 2010 8:19 pm, edited 3 times in total.

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 Post subject:
PostPosted: Nov Fri 19, 2010 7:34 pm 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Ron Ramirez wrote:
gmcjetpilot wrote:

I'll try positioning the antenna horizontally again, and will try a 3 prong to 2 prong adapter, before giving up entirely (hoping Ed finds a solution that I can apply to my TH).


I'm working on it Ron, having a lot of people over for the holiday(s) and want to show off my radios with authentic programming. As soon as I find out what works, you'll be the first to know!

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 Post subject:
PostPosted: Nov Sat 20, 2010 3:41 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 312
Location: Stockbridge, GA, USA
gmcjetpilot wrote:
Antenna - I fixed my hum again but it took stretching the antenna out horizontal. The ground wire out the door into the dirt helps most of the time. Cheers


That sounds like you are picking up some hum off of the power lines in your walls. By putting the antenna horizontal it's at a right angle to those lines and minimizes any inductive coupling between the two.

As I said, I have noticed a varying amount of hum on mine. The ground conductivity where I live is very poor (bedrock is close to the surface) and when it's dry the signal is worse than when it has rained. One of these days I'm going to either get the external antenna kit to put in my attic or just get a long audio cable and put the whole unit in the attic.

Michael

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PostPosted: Nov Sun 21, 2010 6:03 pm 
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Joined: Jul Wed 22, 2009 8:32 am
Posts: 3805
I just found a bunch of info on Part 15 web forums. These are links to individual threads with some info or links I extracted. If you read all this there is good info that will no doubt help. In no particular order of importance.

Why does my Transmitter Hum?
http://part15.us/node/479
http://www.northcountryradio.com/Articles/humred.htm
http://kenneke.com/~jon/pixie/pixietips.html
http://www.bluejeanscable.com/articles/humrejection.htm
http://www.epanorama.net/documents/grou ... rcuit.html
http://www.epanorama.net/documents/grou ... lving.html
http://lists.contesting.com/pipermail/t ... 15534.html
http://web.archive.org/web/200108251945 ... DIY/ground


TH Extensive mods
http://part15.us/node/2419


talking house 2 power supply requirements
http://part15.us/node/1968


Hum in AM Signal
http://part15.us/node/2473


http://part15.us/node/2508
use two 12 volt lead sealed batterys, about 7.5 Amps each. I charge then in parallel but run them in series to a adjustible voltage regulator for what ever the voltage is that is required, 16-18?

I usually just recharge when the transmitter is not being used. This took care of the hum problem with the talking house. ( along with an outside external anttnna) I also run ground loop isolators in the audio leads and a ground wires right to the same point on a cold water pipe from each accessory I have attached to the transmitter ( EQ, SIMA SVS4 Switcher,and audio sources.
Radio Joe


http://part15.us/node/855
It doesn't know the words...
-But seriously folks, hum can be RF from the wire antenna being coupled back into the DC input to the transmitter. A greater value capacitor to ground on the DC input can be a real lifesaver. Also shielded wire and toroid cores are good to have around to decouple audio and DC to the transmitter from a variety of sources, including computer equipment. Also, remember ground the shield only on one end of the wire pair. Other wise you are guaranteed to have a ground loop. And remember, if it won't stop humming you may have to teach it the words.

http://part15.us/node/2484
Then spent 3 days getting the hum out. I had the antenna on my metal roof, and could not get all the hum out till I moved the antenna away from the building.


Further I found this but can't find the jumpers myself:
I rediscovered a fine-point about setting one of them up which I'd forgotten. The subject is grounding, and the three jumpers labeled S1, S2 and S3.

In recent months coverage at 1680 kHz has not been what it once was, and I thought maybe it would be time to think about buried ground radials, a hassle I'd like to avoid, but then I discovered S1, which connects transmitter ground to audio ground, was off, in which case an inductor prevents RF from reaching the audio ground. By simply jumpering S1 the old signal is back again.

S2 and S3 are also jumpered, creating a ground path through the power supply

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 Post subject:
PostPosted: Nov Sun 21, 2010 8:37 pm 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Thanks for all the research Pilot....lots of good reading there. I played with mine ALL DAY YESTERDAY! Varied levels of hum but I never managed to remove it all. There are sweet spots in the house for both the receiver and the TH but it's still not up to my expectations yet. One thing I did notice however was that if I grounded the TH chassis to a water pipe, the hum go REALLY loud.

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There's nothing like the smell of an old, musty radio....


Last edited by ecarfar on Nov Mon 22, 2010 4:14 pm, edited 1 time in total.

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PostPosted: Nov Mon 22, 2010 3:10 am 
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Joined: Jul Wed 22, 2009 8:32 am
Posts: 3805
ecarfar wrote:
Thanks for all the research Pilot....lots of good reading there. I played with mine ALL DAY YESTERDAY! Varied levels of hum but I never managed to remove it all. There are sweet spots in the house for both the receiver and the TH but it's still not up to my expectations yet. One thing I did notice however was that if I grounded the TH chassis to a water pipe, the hum go REALLY loud.

You're welcome. I want to know as well. You're not the only one. My hum comes and goes, but typically I can only hear a faint (1 out of 10) hum with dead carrier and volume turned up. There is a hum but I can live with that. It's not bad enough to make it sound like the radio needs new caps. :shock:

I found one thing today, by moving or rotating the receiving radio, I could make a loud hum! I have some RFI in the house or the interaction with the TH and radio is a factor. The next step is unplug some things and see if I can hunt that RFI down. This night I moved the receiving radio again, and it made no difference? No hum no matter which way it was? I did not change anything. Weird. I had it on all day.

I did not spend all day messing with it, but I did put the whole TH outside on the patio. It didn't really make a difference, but got a huge hum at first when I had the audio, power and antenna kind of twisted together. "Lead Dress" is important. Reading those links I see some use RF chokes or beads. Also good shielded audio cable is something to consider. Next I am going to make an outdoor antenna and use the coaxial and try that. So far I have only used the wire antenna it came with.

I forgot to take the portable radio outside when I had the TH outside. That might have got the hum down to zero.

Water pipe made the hum get loud? Interesting. My house has plastic pipes!

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Tube: AM/FM Zeniths, RCA, TrueTone table tops; Transistor: Kaito KA1103, TenTec RX320D, Pioneer SX780


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PostPosted: Nov Mon 22, 2010 3:40 am 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Really? Plastic water (supply) pipes? Mine are all copper along with the heating system. Regarding your suggestion to unplug things around the house...did that to the Nth degree yesterday...even went so far as to unplug the fish tank pump and airator. Fish didn't like that too much and it didn't help at all anyway.

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There's nothing like the smell of an old, musty radio....


Last edited by ecarfar on Nov Mon 22, 2010 4:15 pm, edited 2 times in total.

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PostPosted: Nov Mon 22, 2010 3:51 am 
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ecarfar wrote:
Really? Plastic water (supply) pipes? Mine are all copper along with the heating system. Regarding your suggestion to unplug things around the house...did that to the Nth degree yesterday...even went so far as to unplug the fish tank pump and airator. Fish didn't like that too much and it didn't help at all anyway.

Yea the service is copper, hot-cold but the drain is all PVC. However in some cases they transition from copper to plastic to go the last bit. Yep new mass produced homes use PVC... at least it's the good stuff, schedule wise and material. My home is moderate fancy and good quality in construction. Copper will last forever, PVC is suppose to last a long time, longer than I will be around.

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PostPosted: Nov Wed 24, 2010 7:21 pm 
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Found some youtube videos that might help set up a nice sounding AM transmitter. These are about the Rangemaster brand but it's gets into generic info that applies to the Talking house.....

Part 15 Rangemaster AM Transmitter Set-up and Upgraded Studio Components
http://www.youtube.com/watch?v=lmzelP_Sobs

In the video above it mentions a PC device to help your audio out of a PC. If you use WinAmp get Stereo Tools plug in, its free and has compression, limiter and EQ.
soundhttp://www.echoaudio.com/Products/ ... /index.php

The other device is a Inovonics Model 222 - AM Compliance Processor, to boost the modulation over 100%, but he says it will only work with the rangemaster and professional transmitters. The TH is not even at 100% modulation I believe. The price is too steep for a hobby, but it is interesting.
http://www.inovon.com/?a=2&s=1&i=1

The other device, an audio interface, in the first minute of the video comes, with the rangemaster. It's an impedance matching pre-amp module that is included with the Rangemaster.

He also shows some fancy compression & limiting hardware and a device to boost the modulation... I don't think the modulation can be boosted on the TH, which is less than 100%.

He also shows a WiFi unit was causing him and others RFI problems. I have the one he says is a problem? I had eliminated the WiFi as an issue, but need to look at it again. I can say the brand he recommends, NETGEAR is a good brand.

Also lots of Ferrite beads or chokes might be another plus.


The video below shows his SYSTEM from a car. His set up uses multi transmitters with the same program, through Internet for large coverage area. He shows one problem, in overlap areas where there is some internet delay, but you can see multi transmitter could cover a large area with part 15 transmitters. This being Sioux Falls I am sure they have less competition. It seems he streams internet radio. I wounder if he sells ads. He implies he does in the video above.

Drive test of Part 15 AM transmitting under fair conditions. Home AM transmitter in Sioux Falls
http://www.youtube.com/watch?v=UjzTP2F1PSE

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PostPosted: Nov Mon 29, 2010 5:54 pm 
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Joined: Sep Wed 26, 2007 2:54 pm
Posts: 502
Location: Long Island, NY
Ok, this thing has be baffled. I turned on the TH Tuesday night playing my iTunes form my laptop and kept it running on 950 KHz for the entire weekend up until Sunday night. The TH, laptop and antenna weren't moved an inch. I also used three different tube radios to receive the signal. Tuesday and Wed. morning the hum was so bad I really couldn't listen to it, Wednsday night it got a little better. Thursday there was a slight hint of a hum, but not too bad. By Friday the hum was completely gone and the signal was loud and clear. I kept it on until last night and the radios all played fine. I'm clueless as to why this is happening and why it seems to get better the lionger I leave it on.

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PostPosted: Nov Mon 29, 2010 8:22 pm 
Silent Key
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Joined: Feb Wed 03, 2010 1:01 am
Posts: 5110
Location: Crawfordsville, Indiana 47933
I am just curious and am going to bow to the more experienced who have commented.

But you said it gets better or the hum gets less the longer you leave the radios on correct? Is this a consistent thing? Every time? If not, it sounds like an outside interference. This idea may have already been discussed and discarded, but I thought I would mention it.

A Ham friend of mine in Kokomo Indiana had interference problems years back. He was going nuts. Had the power company out. Had an electrician check his wiring and service. Nothing. One day he was driving home from some where and passed a factory that was perhaps 3/4 mile from his home. He had his AM radio on in his car. All of of a sudden "crash" the hum about blew out his speakers.

He said he stopped right there. Thought about it a minute. Said what the heck.

He went into the factory and got in contact with the maintenance supervisor. Who, just by chance was also a Ham.

To make a long story short. The 2nd shift came in at that time and started up different machines of some kind. It was found by trial and error that one of them had a serious electrical problem. They fixed it.

My friend got rid of his interference and they saved their machine.

Weird story but true. I swear on a stack of Gerbils.

I'm to lazy to read through the whole thread. I just browsed. Sorry.

:)

P.S. An AM radio is a great noise detector. So is FM if you have an visual audio indicator. (S-meter)

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PostPosted: Nov Mon 29, 2010 8:44 pm 
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Joined: Feb Wed 06, 2008 5:17 am
Posts: 762
Location: Ferdinand, IN
Quote:
To summarize my experience with the TH 4.6:

1. Tried it out upon arrival with factory wall wart (3 prong): Worked, loud hum in broadcast signal.
2. Connected it in different room with computer hooked up to it, loud hum remained.
3. Tried using ground loop isolator between computer and TH. Still hums.
4. Tried using Compaq laptop power supply (2 prong) instead of original wall wart. Still hums.
5. Disconnected computer from TH. Still hums.
6. Transmittted built-in prerecorded message from factory. Still hums.
7. Grounded TH case. Still hums.
8. Broadcast "dead carrier." Still hums.
9. Tried using outdoor longwire antenna. Still hums.
10. Tried moving antenna around. Still hums.

11. Finally tried a 3 prong to 2 prong adapter. Hum is still present, but does not seem to be quite as overwhelming. I think I'll leave mine on for a few days and see if it clears up on its own, as Ed's did, or not.


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PostPosted: Nov Mon 29, 2010 9:40 pm 
Silent Key
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Posts: 5110
Location: Crawfordsville, Indiana 47933
I have absolutely no experience with what you guy are talking about.

From the sounds of your problems, I don't think I want any. I just don't understand how the hum/hiss whatever can just fade away. Sounds kind of like a capacitor is discharging or something. There has to be some reason for it being there.

If you find out what is the cause, I am sure everyone on this thread will be quite interested.



Bill :roll:

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