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THE AM BULLETIN BOARD => Technical Forum => Topic started by: ka4koe on February 25, 2015, 09:45:03 AM



Title: Possible Big TX Lead
Post by: ka4koe on February 25, 2015, 09:45:03 AM
I may have found a BC610 but need some advice...either this or a BC RCA Tx.

1. Must the unit have the BC614 speech amp to work?

That's all I can think to ask as I am in Terra Incognita at the moment. What should I be asking at this point? It is affordable and its not terribly far away. However, if the unit is lacking major assemblies then I don't want to jump on it.

Philip


Title: Re: Possible Big TX Lead
Post by: steve_qix on February 25, 2015, 10:22:47 AM
Get the BC610.  You do not need the 614, and in fact, you will be much better served by NOT using it - and using a good quality audio driver.  Furthermore, you can use an external RF driver (or VFO).  The BC610 internal VFO is pretty bad and suffers from FM hum.  Many BC610s have this characteristic hum on the carrier.

The advantage of the BC610 over an RCA BC transmitter is that you don't have to really build anything that's incredibly complex.  Converting a BC rig to 75 meters is a big job.


Title: Re: Possible Big TX Lead
Post by: W2VW on February 25, 2015, 11:55:20 AM
The later beastie-610 (F model and up) is ugly and looks like an oil burner. It also has much better magnetics.

Look for the tuning units and output coils as you will want to get on many bands.

The gent who used to sweep the TV transmitter feedlines where I work put one on 10 meters at the end of WW-2! So did a bunch of his buddies all over the world.



Title: Re: Possible Big TX Lead
Post by: N8ETQ on February 26, 2015, 10:55:41 AM


   Hey Phil,

      Congrats on the 610(*). It really makes a difference which
model it is. On all models you can get away without the 614 but
starting with the "E" model the Modulator Ip meter was moved into
the speech amp.  The "E" model was the last of the "Pretty" ones,
and the later models somewhat more utilitarian in appearance.

      My Fav. is the "C" model with the Mod current and PA
current meters in the edge Pillar's. The speech amp for the "C"
had a VU meter in it.  Mine also came from a ham who had it
on 10m CW. Only mod was the jack bar for the tank coils was
changed to accommodate B&W coils and a nice 4 turn loop was
improvised for loading. Works well so I never restored it
to original.

     Also starting with the "E" model the Army provisioned
them with coils and TU's to get up to 18Mc, prior to that
8Mc was the top end as far as the signal Corp was concerned.

GL and please keep us posted.

/Dan


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 01:12:37 PM
Price has dropped on unit. Waiting to get photos from the current holder (he's acting for the SK's estate). No idea what version or what coils/plug ins are available. No outboard tuner or speech unit. Its either the 610 or an RCA BTA-1MX.

Philip


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 03:26:19 PM
Photos. Its an H.


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 03:27:01 PM
More


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 03:27:27 PM
More


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 03:28:36 PM
Last


Title: Re: Possible Big TX Lead
Post by: N8ETQ on March 03, 2015, 04:00:19 PM


    Very Nice,


          The "H" was used later in Korea (maybe real late WWII also)
with the GRC-26 RATT set. 610's were a basic component and swapped
for availability and serviceability, but when shipped it was with
an "H".  Here's the Dope on it.

http://rattrig.com/AN-GRC-26/26.htm

          The early "A", "B", "C", variants used Modified 312's
and 342's. It was just a power supply mod with a VR tube for the HFO.
The "D" version saw the T-3 and R-388's..  My "I" Model has a
Manufacture date of 1951..

/Dan



Title: Re: Possible Big TX Lead
Post by: KC4VWU on March 03, 2015, 04:31:26 PM
1 el,
       Looks like it's in really good shape. Do your homework and make sure the M.O. tuning units and final coils are the right numbers you'll need to cover the bands 80 & 40. You'll need some hefty xtals or a signal source, at least some sort of mic amp into the 2A3's (or something to drive the 100TH's), and the TSM w/ schematics.

Either one you choose will be a FB step up; vintage military or vintage broadcast. Both would provide you a lifetime of service with proper care. Get Both!! (opinion of a toob RF junkie.)

Phil


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 04:43:02 PM
Not looking good. This just in...

The Coil Units are as follows:

2 ea C-448-B 11.0 - 14.0 MC

C-449-8 14.0 - 18.0 MC

C-447-B 8.0 - 11.0 MC

80 HNL


Title: Re: Possible Big TX Lead
Post by: WA2OLZ on March 03, 2015, 05:27:24 PM
Not too shabby. We will be listening for you on 20M A.M.  Maybe 14.300?

You are a trooper, One L. First the Valiant and now this!



Title: Re: Possible Big TX Lead
Post by: ka4koe on March 03, 2015, 05:41:34 PM
AM is usually at 14.330. Valiant is working well these days. Not decided to jump on this or not. Lacking lower band coils and no word on oscillator plug ins.


Title: Re: Possible Big TX Lead
Post by: WA2OLZ on March 03, 2015, 06:28:38 PM
True, Phil, but I'm sure you would get the attention of the CB crowd on .300!


Title: Re: Possible Big TX Lead
Post by: WBear2GCR on March 03, 2015, 07:54:29 PM
Assuming you don't mind doing actual work to make a rig play, I'd grab it.

The lower band coils not only come up at hamfests, they are fairly easy to homebrew. The coils, as you can
see are on plug-ins that consist of manly size banana plugs screwed to a bit of ceramic or phenolic, depending
on what you get. You can make this out of lucite/polycarbonate too. It's big enough and simple enough so that you can actually wind ur own out of copper wire.

The TUs also show up in hamfests.

Not sure they are needed for operation - I seem to think they are not. Probably wrong, but maybe not.

Anyhow, I have some TUs sitting in a box that I could part with for the cost of sheeping...

...go for it!!


Title: Re: Possible Big TX Lead
Post by: Opcom on March 04, 2015, 03:18:25 AM
Don't let the coils determine the sale. 

I don't own one of those sets but fiddling with coils is done a lot around here to move something just a bit. Does it work on the 610? Just throwing out some suggestions.

2 ea C-448-B 11.0 - 14.0 MC
-jump half a turn and make it cover 20M? Will it do it as is, at the extreme end? Maybe. only 300KC

C-449-8 14.0 - 18.0 MC OK there's 20M, but try the same trick jumping a turn or two? to put it on 21Mhz/15M.

C-447-B 8.0 - 11.0 MC There's your 40M coil. Add some capacitance across it to bring the frequency down.

That old set probably won't mind small changes in Q or anything else as long as you don't go crazy on it. What say 610 owners on the suggestions? What are the real limitations?


Title: Re: Possible Big TX Lead
Post by: N8ETQ on March 04, 2015, 07:25:16 AM
  I have an extra TU-49 (3.2-4.0Mc) and add turns to
any of your other coils to make it look like this
and your on 75. The links are pretty much the same.

/Dan


The stuff is on epay all the time..
http://www.ebay.com/itm/HALLICRAFTERS-BC-610-COIL-5-7-TO-8-0-MEGS-MINOR-DAMAGE-MYSTERY-COIL-INCLUDED-/201297591821?pt=LH_DefaultDomain_0&hash=item2ede457e0d


Title: Re: Possible Big TX Lead
Post by: W2VW on March 04, 2015, 10:25:45 AM
Easy to make coils. You can even skip the swinging link. Use a fixed link and add a loading capacitor.

You really want the tuning units. I'm sure people are sitting on them.

That tx would really make your signal stand out on 80.


Title: Re: Possible Big TX Lead
Post by: ka4koe on March 04, 2015, 08:19:20 PM
I'm passing on the 610. Gonna get a BC transmitter. If you want the 610, check the for sale section.

Philip
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands