[Hammarlund] B on SP-200 faceplate?

[Al Parker]

Hi Folks,
	You can see the original ad for the SP-200 series "commercial" versions 
at <http://www.boatanchors.org/BC779/images/SP210ad.pdf>
	If anyone wants to follow Bob down the rework road, I have 2 candidates 
for you, assuming you want a bit of a project.  I've had both for 8-10 
yrs, waiting attn.  Both are complete with p.s.
    #1.  BC-779B, covers 100 - 400 kc and 2.5 - 20 mc.  Has dust covers 
for both rcvr & p.s.  All I've done is clean the front panel, it's 
pretty good, and could easily be left as-is.  I don't think I powered 
this up after I got it, from a friend, abt 10 yrs ago.  I don't know if 
he had been into it at all.  It's been stored in my shop since, AC & 
heat when I'm in there, it's attached to the house so is a pretty good 
climate.
    #2  Covers BC band thru 20mc.  It also has a dust cover on it, the 
p.s. doesn't.  Got this from a local guy who'd been in Taiwan 20+ yrs 
ago, it had been worked on, he says, by the Taiwanese shop on base, or 
whatever he was on.  It does show  evidence of recapping, as he said, 
and it has a prod. det. in it already.  The under chassis rewiring is a 
bit rough, storage before I got it probably was in an uheated garage. 
I have not done anything to it, got it 6-8 yrs ago locally.  It does 
have documentation, an original manual plus hand drawn skems. of mods.

     $150 for either one, prefer you pickup, or I can del. to a hamfest 
within 150 mi.
   If to be shipped, I do have crates for each pc, which must have a 
deposit, refunded upon return, but weights make shipping high (no 
upcharge by me, just Fedex or UPS fees).
	I agree with most of what's been said about these, they do make a fine 
band-cruiser.  I did one abt 10 yrs ago, you can see pix and info at 
<http://www.boatanchors.org/SP200.htm>
73,

Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 3/28/2013 1:24 AM, Kenneth G. Gordon wrote:
> On 27 Mar 2013 at 19:56, Richard Knoppow wrote:
>
>>       The BFO injection on mine was reasonable and I used it
>> for both CW and SSB.
>
> I now suspect that the reason the BFO injection was so low on my original
> BC-779 was that there was a defective part, probably the BFO coupling cap.
>
>>   A product detector would help
>
> The one I added didn't just help: it made a simply amazing difference.
>
>> but I
>> think you can improve injection by increasing the value of
>> the coupling cap.
>
> Well, athough I am sure that would help, what I did made a far greater
> difference.
>
>>       The AVC system is such that the BFO is pretty well
>> isolated from the AVC.
>
> Yes. It has its own IF transformer and IF amp.
>
>>       The Geisler mods resulted in low gain. I don't remember
>> what else. Unfortunately, the RF and mixer tubes used in the
>> Super-Pro are very noisy especially the mixer.
>
> Well, yes, but there are two RF amps, at least in the BC-779. After I
> incorporated my product detector, that BC-779 became unusually quiet. The
> two RF amp stages masked the mixer noise almost perfectly. I could hear
> signals on that receiver that I didn't even know were in there before the mod.
> The BC-779 sounded better on 20 meters than my hot-rodded SB-101. The
> BC-779 was quieter and just plain more transparent than the SB-101.
>
> The increase in apparent sensitivity would have to be heard to be believed.  I
> was truly amazed.
>
> I have always wished I had been able to do a before and after comparison of
> sensistivity and signal-to-noise ratio. At the time, I simply didn't have the
> equipment.
>
>> It taks some
>> care if you want to re-design the front end that you don't
>> wind up with overload problems and spurs.
>
> Yes, but it can be done.
>
>>   Somewhere I have
>> a Signal Corps technical manual (don't remember the number)
>> which has details of all the receivers used at the time (mid
>> 1940s). One set of charts shows image and spurious responses
>> of the Super-Pro and SX-28. The Super Pro has only one
>> image, quite low, while the SX-28 looks like a corn field.
>> I've been trying to find this book in my stored stuff with
>> no success so far, but its there!
>
> Well, when you find it, I am sure that there are many of us out here who
> would LOVE to read it.
>
>>       FWIW, the RF amplifiers in the BC-1004, the 40 mhz
>> version of the Super Pro, are shunt connected instead of
>> series connected as in the other models. I think this was
>> done to improve the Q of the coils by getting any DC
>> magnetization off of the iron cores.
>
> That IS interesting, all right.
>
>>   The Super Pro is also
>> one of the few receivers that have genuine Faraday shields
>> on the antenna coils. They are woven metallic cloth between
>> primary and secondary of the coils. You can see them if you
>> take the bottom cover off the coil compartment.
>
> Yes. I have seen them.
>
>>       The broadcast band and LF bands are also broad banded
>> using resistors. Otherwise the bandwidth is not as wide as
>> the IF.
>
> 16 KHz... :-)
>
>>       The Super Pro seems to be the most expensive receiver
>> on the general market but the RCA AR-88 was probably double
>> the price. Most, if not all, AR-88s were sold to the
>> government.
>
> A large percentage were shipped to England. I have never had the
> opportunity to use an AR-88, but have always wanted to.
>
> Ken W7EKB
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