Re: {Collins} Difference between 75S-1 and 75S-3



Glen, Bill... what about the change in the BFO xtal frequency near 455 kHz
from the standard issue in the -3 equipped with 200 Hz. CW filter?  I do
pretty much CW and the issue with the 200 Hz filter once tuned properly is
the CW pitch is too high for my taste. If CW is a favorite mode of
operation, I would recommend the altered xtal freq. Sorry, would need to
look it up, not at my finger tips the xtal frequnecy. Alan

On Sun, Oct 29, 2017 at 8:30 AM, Glen Zook via Collins <
collins@xxxxxxxxxxxxx> wrote:

> I slightly disagree!  The 75S-3 is the 2nd best of the 75S- receivers.
> The 75S-3A is the best! :>)  Of course, the only difference between the
> 75S-3 and 75S-3A is the additional crystal deck but having those additional
> crystals does add to the functionality of the receiver.  The performance of
> the 75S-3 and 75S-3A is identical.
>
> Every 75S-3 and 75S-3A  came from the factory with a 200 Hz CW filter
> installed whereas the 75S-1 / 75S-2 had an optional 500 Hz filter that had
> to be installed after the receiver was purchased (this by decree of Art
> Collins) by returning the receiver to the factory, having the filter
> installed at an authorized service center, or the filter, and optional BFO
> crystal, were available to the end user so that anyone could do the
> installation.  In the 75S-3B / 75S-3C all CW filters were available at an
> additional charge.
>
> By the way, the 200 Hz filter is a crystal filter, not a mechanical
> filter.  Also, there are a very few amateur radio operators who remove the
> 200 Hz filter from the 75S-3 / 75S-3A when selling one of those receivers.
> The filter is then offered individually with the seller "claiming" that the
> filter was an optional accessory.  This is absolutely false!  Every 75S-3
> and 75S-3A receivers came from the factory with the CW filter installed.
>
> I have owned a 75S-3, do own 2-each 75S-1 receivers, and my primary
> receiver is a 75S-3A.  Also, I work on Collins equipment for others and
> have seen a fair number of 75S-3B and 75S-3C receivers.  I definitely agree
> with Bill that the 75S-3 / 75S-3A receivers are better than the 75S-3B /
> 75S-3C and considerably better than the 75S-1 / 75S-2 receivers.
>
>  Glen, K9STH
> Website: http://k9sth.net
>
>
>
>       From: Bill Carns via Collins <collins@xxxxxxxxxxxxx>
>  To: 'Brian Gieryk' <ke6iyc@xxxxxxx>
> Cc: COLLINS@xxxxxxxxxxxxx
>  Sent: Saturday, October 28, 2017 8:10 PM
>  Subject: Re: {Collins} Difference between 75S-1 and 75S-3
>
> Hmmmmmmmmmm - Functional difference..  On the most basic level - NONE!
> They
> are both receivers.  :-)
>
> On a performance level - DAY & NIGHT.  The 75S-3 is so much better a
> performer that you will not ever go back to the S-1.  Do not misunderstand,
> the 75S-1 is a good (not great - but good) receiver - but the 75S-3 is so
> much better.
>
> On a more detailed level,
> 75S-1 w/ 10 tubes (stripping away the Xtal Cal, the injection and PTO Osc
> and the PTO Cath follower leaves):
>       RF Amp, 2 Mixers cascaded, 2 IF amps w/ Mech Fil. And either Product
> or AM Detect/AGC rectifier combo and then one audio Amp.
>       Thus, the basic receiver is 1 RF Amp, 2 Mixers, 2 IF amps w/ Mech
> Fil.
> Loss and the detector and Audio amp
>       Performance results from 7 stages, 3 of which have gains less than 1
> -and then mechanical filter losses.
>
>       The 75S-1 has no notch filter, no variable BFO
>
> 75S-3 w/12 tubes
>     The same stripping away with the 745S-3 gives another stage of IF gain
> (now essentially 3) combined with notch filter and separate AGC rectifier
> and two stages of Audio gain. The technical result is better gain
> distribution, selectivity,  audio out and AGC performance
>
> The results are dramatic.  It is often stated that the 75S-3 is the best of
> the S-Line receivers and I agree.
> It has the variable VFO/Fixed BFO feature, Notch Filter (Aka Q-Multiplier)
> and selectable AGC time constant (not found on the S-1).
>
> While the 75S-3B/C is more "sophisticated with plug-in filters, it is with
> the sacrifice of skirt selectivity.  In addition, the entire Gain
> Distribution and AGC performance is somewhat less than the 75S-3 in my
> opinion.
>
> I have attached the Sherwood Engineering Receiver Comparison Data (Highly
> respected) for the S-3 and S-3B/C and while the filter rejection and
> dynamic
> range may look better for the 3B/C, I can tell you that in use, the 3 will
> win your heart hands down.
>
> Make sure when you look for an S-3 that it has the CW mechanical filter.
> It
> was an option in the S-3.
>
> I apologize to the list as I know that the file will not go through, but
> the
> data is readily available at: http://www.sherweng.com/table.html
>
> Have fun in your hunt!
>
> Bill
> Bill Carns, N7OTQ (Trustee K0CXX)
> Past President, Collins Collectors Association
> Founding Board, Collins Radio Heritage Group
> Editor, Signal Magazine (Retired)
> Wimberley, TX
> 512 618 2762  (Cell)
> 512 847 7010  (Home)
>
>
>
>
>
>
> -----Original Message-----
> From: Collins [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx]
> On
> Behalf Of Brian Gieryk via Collins
> Sent: Saturday, October 28, 2017 10:58 AM
> To: collins@xxxxxxxxxxxxx
> Subject: {Collins} Difference between 75S-1 and 75S-3
>
> Apologies in advance, as I am new to the world of S line equipment (but not
> radio in general, nor HF-80 equipment).
>
> What is the functional difference between a 75S-1 and the 75S-3?
>
> Thank you!
>
> Brian
> KE6IYC
>
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