The second TH 2 came in today and i have started to experiment with the antenna placement and setting the audio.
The second TH 2 came in today and i have started to experiment with the antenna placement and setting the audio.
First the audio seems a bit flat, mid range and highs are good but bass response is poor.
Second the range is decent although i haven’t really tested past the mobile home park, but in some areas the signal is weak and others the signal is listenable. (using the wire antenna)
In weak areas my car radio is bombarded with static and buzzing wich has nothing to do with the TH2 it’s just environmental noise. Powerlines and Cable TV.
100 feet from my tin can and the signal is great, no static and listenable tone quality. I have to assume this has been said before, the TH2 is more suitable for voice.
At any rate, more experimenting is needed before i put the TH2 in permanent service.
Poor range from TH2
Range so far during the daylight hours was just under 50 feet from the outside of my house.
At night it’s just outside the home at close to 20 feet.
I am guessing this mobile home siding is blocking alot of the signal from leaking out of the house wich is something i was sure would happen.
The transmitter is close to a window with the antenna stretched out as vertically as i can get in a confined space.
Inside it’s strong of course.
At this point i am really starting to wonder if going AM is going to be worth the trouble.
Whip It, Whip It Good!
The outdoor ATU that connects to the TH works pretty good and is not very noticable. A standard 102″ CB whip attaches to the ATU which mounts on a standard 1 1/4 to 1 1/2″ mast.
I finally got a basic schematic for the TH and it has the schematic for the ATU also. The ATU is very similar to the tuner built into the TH except it’s all manually operated.
There are two loading coils with ferrite slugs that slide in and out of the coil forms when you turn a knob. A two position switch selects one or the other depending upon which end of the AM band you are operating on. It also has a simple RF strength meter consisting of a micro-amp meter and a few resistors, capacitors and diodes. The meter shows when the correct tuning has been reached for maximum signal output.
Unless you have some pretty nosey neighbors I don’t think anyone would notice. Maybe you could mount it on the car when you go on the air. Tell ’em you have a CB in it.
Scavenging time?
That’s great info, MRAM. Of course, everyone would love to see those schematics so I hope you’ll post them.
Your description of the ATU makes me wonder if I shouldn’t open up one of the TH XMTRs I got from ebay and scavenge the tuner section for a home-made ATU…
Talking House Diagrams
This link takes you to the TALKING HOUSE TRANSMITTER DIAGRAMS.
The document contains patent information and several diagrams of the transmitter. It is broken down into sections, block diagrams and schematics.
Page 10 details the ATU. I’m sure the transmitter may have undergone modifications along the way so consider these schematics as conceptual in nature. But, they appear to be fairly close if not the actual item.
The PDF file requires the free Adobe Acrobat Reader found at Adobe.com.
The link to the Free Patent site was found through a search on this website. Thanks Part15!!!
Awesome Find!
Great work MRAM!
That maybe the answer i am looking for and no i am not too worried about my neighbors lol , they probably have already noticed the dipole on the porch for FM and no one’s bothered to complain.
Beside the owners of the park already know what i am doing and haven’t complained yet.
I downloaded the pdf/plans for the atu and will see if i can adapt them for my needs here. It’s pretty clear to me that the siding is not allowing enough signal to leave the house so I will have to go with some kind of outdoor antenna for AM.
Also ive noticed that the modulation is a bit low on this th2 and will be replacing the fuse in the second th2 so that i can compare the modulation levels between the two. (the first unit had a bad fuse when i received it). Another thing that would help my range is trying other frequencies beside 1630 khz.
1630 seems to have traffic on it now during the day, I can hear kcjj and another station i cant identify yet. Both stations seem to take turns being heard here.
1620 seems ok but occasionally has a whining noise and what sounds like maybe a TIS. If i had a radio with a meter i’d guess it would read 1 or 2 s-units.
Anything from 1630 khz to 1700 has traffic.
1600 khz has a new station out of Corbin,KY so 1610 is out of the question. I’ll have to listen on the radio in my minivan to see what other channels are clear, that factory stereo is very sensitive.
The only drawback is my car stereo skips 1705 and goes right to 1710.
So it’s trial and error until i find something that works, but for plug and play, the TH2 aint half bad.
1610
1610 was supposed to be kept “0pen” but recently I have heard BC stations on it here in Minnesota, also the Dept of Natural Resources has a VLP transmitter on it 24/7 . The broadcast is worthless and you can barely understand it, the audio is so muddy.. Any way, great info on the schamtics, I downloaded them and printed.
Radio Joe
1600 am kills me here
Am 1600 wkfo corbin/london ky started broadcasting 24/7 now in my area and they seem pretty powerful. They transmit with 1 kw daytime and 27 watts nighttime non-directional signal.
So that leaves me with channels below 1580 and above 1620 khz.
I havent tried building a outdoor antenna yet, our weather has been pretty crummy the past couple of weeks.
One of my TH2’s has trouble tuning up on 1700 wich i may try to lubricate the gears as mentioned in another thread here.
I can hear it somewhere around 1700 to 1710 so im thinking the tuner is overshooting 1700 khz. Any channel below 1600 sounds pretty good and has great sound and a better signal . Still not enough to get out of the trailor past 50 feet. After that the signal fades into the noise.
Most of the noise is from powerlines that stop 50 feet from my house and are fed into underground conduit feeding the rest of the park.
I am going to set up the TH2 on a nice day out here on the front porch to see what kind of coverage i get that way.
Top Band Tuning
Three of the five TH 2’s I bought recently also fall short of the top end of the band stopping at around 1680 kHz. Not that the auto tuner doesn’t tune rather the oscillator won’t go any higher. Besides, on the external antenna the auto tuner is out of the circuit anyway.
When I have time I’ll see if I can locate the VCO of the PLL and with the help of that schematic determine if the control voltage changes with the digital display. I can input frequencies up to 1710 kHz but the output frequency stops around 1680 kHz. If the control voltage stops changing even though the digital display reads higher then there’s a problem in the PLL. Must be a common problem as 3 of the 5 have it.
With regard to the TH auto tuner, 4 of the TH 2 tuners would get stuck. Lubricating didn’t help. I had to disassemble the rack and ream out the plastic piece that slides on the metal rod. In one case I also had to lightly clean inside one of the coil forms with garnet paper as the ferrite rod was sticking.
Too Bad too
The TH2 that has the tuning trouble has way better audio response than the one that tunes 530 to 1700 khz.
The one that seems to tune the whole band has almost a flat audio response, there is a lack of bass, but the midrange and treble seems decent.
Both just dont have the juice to get out of the mobile home but all thru the house it sounds loud and strong. I think if the weather is good this weekend i will place one of the TH2’s out on the front porch wich is 4 ‘ off of the ground.
This way i can see for sure if it is the siding on the home that is keeping the signal in the house. With the TH2 inside, i am lucky if i can hear the station 50 ‘ outside of the house.
I may tinker around with the tuner and see if i can tell what is holding it back. I think the last time i tried to tune up to 1700 it took alot longer to tune up and made more noise than usual.
Inside Job
I took one of my TH2’s to work with me and set it up in my office. The building is a 1930’s vintage brick with steel superstructure. My area is right in the middle of the one level commercial type building which is about 60′ by 180′.
With the wire antenna on the internal tuner, I can hear it about 300′ in most all directions. The signal definitely follows the power lines.
I’m using Zara 1.4.4 with the Sound Solution plug-in so I can boost/cut the frequency response with its 5 band eq. It had a lot of hum until I unplugged the wall wart from the UPS and plugged it into a regular AC outlet.
1705?
I must have been asleep when i posted that? I used to use a dx-390 shortwave receiver all the time before lightening took it out, a great radio and you could use it like a fancy frequency counter since you could choose the steps it tuned.
So what about grounding? We know the TH2 grounds to the outer tip or negative side of the power adaptor, but is that enough grounding?
Perhaps grounding the TH2 to the ground rod on the phone box outside my house would add more ground to the transmitter and increase my coverge.
I also thought about placing the TH2 in a weatherproof case of some sort , feeding audio and power to it then running it outside on the front porch. Im just not sure about running coax and a outdoor antenna to it. That seems like a grey area.
🙂