[BC] Gates BC-1F

[Milton R. Holladay Jr.]

Phil, I had a feeling that you would have a few words to say about this
post; I do, too:
----- Original Message ----- 
From: "Phil Alexander" <dynotherm at earthlink.net>
To: "Broadcast Radio Mailing List" <broadcast at radiolists.net>
Sent: Sunday, May 22, 2005 10:53 PM
Subject: Re: [BC] Gates BC-1F


> On 21 May 2005 at 9:39, Chris Edwards all560 at yahoo.com wrote:
>
> This is a bit stale, but since it's a topic near and dear,
> I'll try to reply. I do love the old BC-1F, not because I
> found the audio that great, but because it was a real moose
> on the RF side and reliable as a Swiss railroad.
>
> > http://lists.radiolists.net/pipermail/broadcast/2005-March/004586.html
> >
> > Uh,  Phil,  have you ever actually HAD one of those
> > UTC LS 1kw mod transformers?
>
> No, I never got the chance. Maybe that was a good thing
> according to your comments. <g>

I never saw any UTCs in use anywhere.

> > And driving 833's with beam pentode 807's in a cathode
> > follower to replace two class-A, direct-heated 845's
> > with the perfect combination of input,  driver,
> > modulation transformers and reactor??????
>
> Yeah, because my experience was far from perfect, and I
> later found good reason to believe my experience was not
> unique. Secondly, they weren't ALWAYS class A, they were
> often AB1 verging on AB2.

Needed to change the cathode(?) resistor from 1500 to 1000ohms and put in a
pot to balance the 845s.
>
> To appreciate the reason for the change you need to have
> some play time with the good GREEN boards used in the
> BC-1G. Static AND dynamic balance were simple with the
> addition of a couple of pots. <g>
>
> > Come now!   The BC-1F was totally unique in all the
> > world.  And I still have the 15 ips reel tapes from
> > 1965 to prove it!
> >
> > Anyone who ever had a 1E knows why the 1F was built in
> > two cabinets.
>
> > And anyone who ever ran a 1F for years,
> > then lost a modulation component and had to live life
> > with the poor substitute of those used in the 1J,  1T,
> > 1G or 1H knows what I mean.

AFAIK, they were just fine.
>
> I ran a fair number of audio proofs on the 1F and was
> never that impressed with the results because the
> modulator was not great at 30 Hz nor was it very
> efficient above 10 kHz.

Needed to put in a much better plate choke and change the .002 cap on the
modulator line to .0005 or smaller
>
> > To me,  the name "Basler"
> > (like "Orban") will always be profane.

Both some of the best. They should sue you. .
>
> Just curious, where do you put Chicago and Electro in
> this  pantheon? There was a period when much of Gates
> iron came from them, and ISTR some of it went into 1F's.

Don't forget Moloney; they made some of the best iron used by Gates. WAGS
has a mod choke in use every day. Chicagos tended to go bad early or last
forever.
>
> I don't think you should hold Bob responsible for
> filling a demand of the industry and doing it better
> than many others of the day. I don't think there are
> ANY AM stations that would trade a 9200 for an SA-39.
> <g> Bob and Frank have both done their part to keep
> listener acceptable sound quality on AM as the
> adjacent channel and power line interference have
> made that more and more difficult.
>
> Time marches on, and our choice is doing the same or
> being left in the dust of history.
>
> > "Thordarson" - now there's a name to reckon with.
>
> Since the 1F I did most of the work on was not that far
> away from them, I got to know them quite well, and
> agree they were really great; not only the iron, but
> their service was outstanding. I even had the president
> of the company show up as the emergency delivery man one
> Sunday afternoon when I was off the air. Although the
> name survives, alas, it's no longer the same company.
> Their bread and butter was TV, and when it stopped using
> their iron, that was the end of a great tradition.
>
>> > Sure, all the later transmitters had better specs.
> > With a sine wave.
>
> For better or worse, we lived and died with the sine
> wave performance because that is what the FCC demanded.

Most circuits that measured really good with sine waves sounded good, too.
(Occasionally, someone would manage to design something that had bad IM but
good sine distortion; It took solid state stuff for transient IM to show
up.)
>
> > But,  do you know,  I spent my
> > late teens with a BC-1F,  and have been trying to get
> > back to that sound ever since?  And I've had them all.
> >
> > By the way,  the 1F did quite nicely out to 15khz
> > under dynamic conditions.
>
> Not in my experience, but that may have been a variation
> in boxes.
>
> > The modulator overloads
> > were slow dashpots,  and typical plate current
> > excursions of an amp or better per tube on highs were
> > common.
>
> I've seen I(mod) L and R pegged out and the plates
> varying between orange and yellow dynamically on a
> 1F playing "The Theme from Mondo Cane." That was the
> one with a lot of HF organ in it, and it did test the
> modulator of any transmitter.
>
> > Still,  the 833's lasted years,

Some, back when tubes were "good", would last several years, some 5 or so.
Had a Westinghouse that must have run for 10 yrs before it started to sag a
tad.
845s were a different story.
>
> If you wanted to pass a proof with something other
> than a pencil, they didn't.
>
> > and the 845's decades.
NOPE! nada chance.
>
> The problem wasn't the tubes it was the driver xfmr.
> Once I put in Thordarson's the performance was better
> on THD.
This is where the 807 driver really shined. A BC-1T in good shape sounded
much more "live" and "open",with excellent highs and lows.
>
> > The feedback complimented the iron perfectly,  and
> > the result through a reasonable AM receiver was
> > astounding.  Loud,  crisp,  and with a way of
> > handling lower mids that Gates/Harris never
> > again achieved.
Distortion often make audio sound "crisp" and loud. The BC-1F audio driver
had a tad of compression non-linearity (distortion). (I posted considerable
a year or so ago about modifying it for better linearity.)
>
> I liked it because it was a reliable moose that was
> easy to get in and work on, but was never that
> impressed with its audio high end. In those days I
> could hear out to about 19.5 kHz and did some
> interesting sound work for people like Johnny Cash
> and Ray Charles before groups traveled with trucks
> full of sound gear. There's no denying that the 1F
> was meant for rock, but for overall sound quality,
> I'd have to give the nod to the Vanguard, which was
> anything but a moose.

Yes, reliable; a great old box !
>
> > RCA did.  Once.  In the 1MX.  But it
> > was only close,  and harder than the 1E to maintain.

The audio circuit in the BTA-1MX was virtually identical to the BC-1T and G.
The problem with the BC-1F was TILT (phase shift) which was much less when
the driver xrmr was omitted.(Can you say Volumax 400 ?)
>
> I never worked on one, but I understand the basic
> design originated with Raytheon in the RA-1000.

No. Did you know that the audio circuit in the RA-1000 was identical in
design to that in the BC-1F?  But the RA-1000 had two 813 RF drivers and
push pull RF PA. May have even been a better box than the BC-1F
>
> Part of the "magic" was the heavy RF drive from the
> 813. It could develop all the 833's needed on positive
> peaks.
>
> > Today,  of course, it doesn't matter.   All audio is
> > being processed (and programmed) to replicate the
> > sound of 3-bit PCS.  And,  with every technical
> > "advancement",  radio recedes further into the QRM.
> > But it was once great.  And I have the tapes to prove
> > it...
The 10kc NRSC cutoff was the end of it.
>
> There are cycles both in human preferences and in
> technology. Once full digital becomes a fact and a few
> years are spent on codec improvement, we may again see
> quality sound on AM. The only question is finding
> quality material that also attracts and audience. I'd
> much rather live in the future than the past, you see.
>
> Phil Alexander, CSRE, AMD
> Broadcast Engineering Services and Technology
> (a Div. of Advanced Parts Corporation)
> Ph. (317) 335-2065   FAX (317) 335-9037
>
It seems to me that Chris is suffering from stopped clock effect
M