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 Post subject: Harvey Wells Transmitter comments sought
PostPosted: Mar Mon 12, 2012 3:19 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 417
Location: North Logan, Utah, USA
Greetings,
Picked up a quite nice TBS-50C transmitter. It has the modulator in it for AM. Someone removed the 6L6's but I have plenty of spares.
It's also had a SO-239 installed where the ceramic feedthru was. Other than that it's pretty much stock.
No power supply or VFO. I'm considering putting this thing on the air. But, wanted to get some feedback on the transmitter.
Is it worth it? 50 watts of AM doesn't seem like enough. And is it a respectable sounding rig? Worth building up a power supply for?
Anyone use one of these on the air? Comments, criticisms on the rig welcome!!

Thanks.

Wally Gibbons, WB7ASQ
North Logan, Utah

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Wally Gibbons, Wally.gibbons@gmail.com


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Mon 12, 2012 11:59 am 
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Joined: Feb Thu 07, 2008 5:58 pm
Posts: 23
I have two TBS50D' s and my original rig in the 50's was a TBS50C. The C model requires a carbon microphone, or an add on preamp such as what is installed in the D model. Power supply is nothing fancy, just a good 450V 150 mA supply. I have the original PS and VFO and the PS uses 2 5U4 tubes. Rig probably puts out about 35 Watts on low bands, less on 10.

Back in the old days I used an old 2-6L6 Heath Hi-Fi amp as the modulator. I just disconnected the output transformer and fed the audio into the 50C modulation transformer. Worked great with standard dynamic mic. Fun little rig.


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Mon 12, 2012 12:36 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 7997
I agree with Bill, it is a fun little rig. I bought a nice TBS-50D model with APS-50 supply several years ago and have it paired with a SX-71. Two years ago I found another TBS-50D with the VFO base and power supply and it is paired with a HRO-7.

At 50 watts input it is about 3 db down from a Viking 1 or 6 db down from a Viking Valiant. To put that into perspective most receivers are calibrated at around 6 db per S unit so if a Valiant were S-9 your TBS-50 would be a very readable S-8. There are certainly times when every bit of power counts but a lot of AM contacts are made on all bands, including 75/80 meters, with far less than legal limit AM rigs. On Saturdays when I am net control on a 75 meter AM net I use either a Johnson 500 or Ranger/Desk KW combo running at the 375 watt carrier output AM legal limit so it is easier for net members to copy but a lot of the check-ins are running "entry level" AM rigs including DX-60, Knight T-60, barefoot Rangers, and other low power transmitters and copy is generally very good on 75 on Saturday mornings. One station often checks in from the Rockford IL area (about 140 air miles from me) using interesting low power rigs in the 5 to 10 watt input range and he is often over S-9 on my SX-88 receiver.

In conclusion, put your TBS-50C on the air and enjoy some AM contacts. I have never used mine on 2 meters other than to confirm it will put out some power there but it has been used a lot on 80, 40, and 10 meters. It was a pretty good trick to produce a mobile rig capable of 80 through 2 meters (160 with modification) back in those days. So long before the modern mini-rigs from Japan Harvey Wells produced maybe the first "DC to daylight" rig.

Rodger WQ9E


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Tue 13, 2012 3:33 am 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 11481
Location: Southern NH, 03076
The C model didnt sound good in the 50's and its no improvement today. Adapt a modern low impedance mike and enjoy it. I ran a TBS-50D mobile for a few years in the late 50's.

These days I have an ART-13 which also used a carbon mike and the first thing I did was to change over to a dynamic mike circuit. I didnt get the rig to sound like I was in a B-17 but to sound good on ham bands AM.

Carl


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Wed 14, 2012 7:51 am 
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Joined: Jul Sat 23, 2011 9:33 pm
Posts: 1015
Location: Long Beach Ms. USA 39560
Please check the bypassing.
When I was a kid, I was advised that the Harvey-Wells rigs were TVI generators. Use a good low-pass filter and modern disk ceramics for bypassing and enjoy it.
Pat

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Pat W5THT
Unhappy tubes blush while unhappy power FETs scatter plastic


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Wed 14, 2012 12:36 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 7997
Of course the good news now is TVI isn't an issue in most places. You generally won't bother satellite and cable systems. I guess the few users of off the air digital TV might be bothered if you live next door to someone using an antenna.

Now the bigger challenge is RFI to amateurs from all of the cheap garbage coming out of far east with switching power supplies, particularly chargers, creating all sorts of RF hash. Plasma televisions are another source of broadband noise and a couple of friends get wiped out by treadmills in their neighborhood. Even in my very rural location I get intermittent interference that takes my noise level up a couple of S units on 80 meters but I can null it with a loop.

Rodger WQ9E


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Thu 15, 2012 12:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 417
Location: North Logan, Utah, USA
Thanks to all for the comments. I'm going to reduce my power transformer spares stock and build up a supply for this little girl, and put her on the air.
I already have a small external mic amplifier that will drive the push pull 6L6's nicely.
80 meter AM here I come.

Then I get to build a linear for it. I have a nice used 4-1000 in good shape just sitting in a box on the shelf that would be perfect :).

Wally

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Wally Gibbons, Wally.gibbons@gmail.com


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 Post subject: Re: Harvey Wells Transmitter comments sought
PostPosted: Mar Thu 15, 2012 5:02 pm 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 11481
Location: Southern NH, 03076
That sounds like an ideal combination to get a good signal on a noisy and often crowded band.
I have several low power rigs that drive a common linear to 300+ W although usually use higher power plate modulated all the way starting at 100-120W and driving amps when needed to clear a hole.

Carl


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