Re: {Collins} Receiver test data, Sherwood


I don't think anyone would argue about the excellence of Collins S-Line receivers in a typical amateur operating environment. Selectivity and sensitivity (5dB noise figure of the S-Line is better than most of the modern receivers) is very good. In my experience, what transpired over the decades was that typical specs such as these became easy to achieve in modern HF/VHF/UHF receivers, but government/military end-users desired increasingly better DR3 performance to optimize operation in their high-occupancy and/or channelized RF environments. To that end, they began to increase receiver DR3 specifications to higher and higher levels. This is what I saw in government Requests For Proposals over my career. The DR3 spec, and how to achieve it, became the driving factor in the design of the receiver. I believe it is for this reason that it made sense for Rob Sherwood to rank his extensive receiver database in order of DR3. As a designer, it is my opinion that high DR3 is the most difficult of the typical RF specs to achieve.

One thing a critical observer of Rob's data might note is that there is a tradeoff/compromise between optimizing DR3 and sensitivity (noise figure) that can be employed in a receiver design. That is why you often see receivers with high DR3 that have relatively poor noise figure. It can be a balancing act to figure out the best design to meet the customer's specs.

Don, W5QN

-----Original Message----- From: kc9cdt--- via Collins
Sent: Friday, September 30, 2016 9:20 AM
To: brloper@xxxxxxxxx ; dukeshifi@xxxxxxxxxxx
Cc: COLLINS@xxxxxxxxxxxxx
Subject: Re: {Collins} Receiver test data, Sherwood

IMHO...forget the list...the Collins in a NORMAL atmospheric conditions works as well as almost all of them...these are lab tests and while interesting and in certain conditions (contesting and maybe if you are trying to work a weak DX right next to a +20 guy) they do mean normal day to day use the Collins, Drake and almost all of the vintage stuff is excellant even today. I have made many A/B tests with many radios and the Collins usually does well.

Antennas is where its at any ways (of course propagation has to be there).

It is said the 75S-3 is the best technically...but I have has em all and they are all outstanding to this day.

Enjoy Collins....some of the best radios on the planet...even today!


Lee Simmonds
Summit DCS

260-403-6936 Cell

-----Original Message-----
From: Ben <brloper@xxxxxxxxx>
To: Gary J FollettDukes HiFi <dukeshifi@xxxxxxxxxxx>
Cc: Collins CCA Reflector <COLLINS@xxxxxxxxxxxxx>
Sent: Thu, Sep 29, 2016 8:44 pm
Subject: Re: {Collins} Receiver test data, Sherwood

I've been to the comparison page but I didn't realize that was a ranking. I thought it was a random list of each receivers measurements. Next question are the rankings by best all around, because I saw the 75S-3B had really great sensitivity so I wondered how it stacked up against the receivers at the top of the list. I guess I need to go back and look at the list again or maybe I was looking at the wrong listSent from my iPad> On Sep 29, 2016, at 7:27 PM, Gary J FollettDukes HiFi <dukeshifi@xxxxxxxxxxx> wrote:> > There is no doubt that he knows more about receivers than just about anyone else. That is why I often look to his information when I am trying to learn.> > However, I do make measurements all of the time, of a more critical nature, for my work, and thus I always have the concept Gauge R&R in the back of my head when I see comparisons between something producing a 104 dB reading (for any test parameter) and 105 dB. I would submit that those two receivers are the SAME and not try to rank them in order. It’s a tie…> > > Gary> > > > >> On Sep 29, 2016, at 12:37 PM, Dave Bottom <ars.kd6az@xxxxxxxxx> wrote:>> >> Back in 2009 when restoring my 75S-3B I was really pleased with the results except that there was virtually no perceptible difference between Fast and Slow AGC compared with my 75S-1 (from the 1970's) and I ran across some interesting material on the Internet about specifically my issue. >> >> I sent an email off to get some further insights, not recognizing Rob's new call sign. It was only after a couple of exchanges and talking with him on the telephone I realized who I was talking with. >> >> Rob does indeed own Collins gear, at least an S-3Line when I talked with him and I could tell he enjoys using it. The 75S-3B tested was undoubtedly his own well tuned receiver. The 75S-3C might have been someone else's and he may have not been inclined to mess with that person's radio, but since he is so approachable, just ask him!>> >> By the way his input on tweaking my 75S-3B's AGC so it was Slow for SSB and Fast for CW or AM was a huge success. It was just as I was expecting it to be.>> >> 73 Dave WI6R>> >> Sent from my iPhone>> >> On Sep 29, 2016, at 9:22 AM, Michael Tortorella <w2iy@xxxxxxxxxxx> wrote:>> >> Granted that the test must be somewhat time-consuming (so it would be>> difficult to expect Rob to undertake as many tests as needed to get a>> reasonable statistical result), Gary's point about the small sample size and>> unit-to-unit variability is indeed well taken. The Holmdel ARC (K2DR) at>> Bell Labs did something similar back in the late 1970s, making some MDS and>> DR3 measurements on receivers owned by members of the club. We had a>> similar experience, lots of unexplained strange results, many probably due>> to not aligning the units before the test. It was fun, though, and>> certainly early days not long after Wes Hayward's article in QST on the>> matter. Somewhere I have a table of the results we got, if anyone is>> interested I can pass it along.>> 73>> Mike W2IY>> >> -----Original Message----->> From: Collins [] On>> Behalf Of Gary J FollettDukes HiFi>> Sent: Thursday, September 29, 2016 12:05 AM>> To: Don Jackson>> Cc: Collins CCA Reflector>> Subject: Re: {Collins} Receiver test data, Sherwood>> >> Thank you for the response, a well spoken response I might add.>> >> I'll read the referenced article as well.>> >> Gary>> >>> On Sep 28, 2016, at 9:57 PM, Don Jackson <w5qn@xxxxxxxxxxx> wrote:>>> >>> Hi Gary,>>> >>> Ah yes, Rob Sherwood's receiver data is interesting, and I spoke with him>> a couple of years ago before writing the article on dynamic range that>> appeared in Q1 2016 Signal magazine. Yes, 2-tone dynamic range has become an>> increasingly important differentiator among receivers over the years because>> it is a good measurement of how well a receiver performs in a crowded signal>> environment.>>> >>> Rob did not test many Collins units (maybe only the ones listed), and more>> unfortunately, did not record the status of service bulletins performed on>> the units. In a nutshell, SB1 and SB2 affect the DR3 performance. SB1>> improves DR3 by reducing the gain in front of the IF filter. SB2 improves>> DR3 by adding selectivity prior to the mechanical filter, which,>> unfortunately, contributes to 3rd order distortion. If you haven't read it,>> I recommend that you check out the article, and you will see comparisons of>> various S-Line receivers with different combinations of service bulletins.>> As well, the article describes how changing to an Inrad mechanical filter>> will improve DR3.>>> >>> If you have further questions, let me know and I will attempt to answer>> them.>>> >>> Don, W5QN>>> Technical Editor, The Signal>>> >>> -----Original Message----- From: Gary J FollettDukes HiFi>>> Sent: Wednesday, September 28, 2016 8:46 PM>>> To: Collins CCA Reflector>>> Subject: {Collins} Receiver test data, Sherwood>>> >>> I am always out to learn and the best way to do so it to ask hard>> questions and learn from those who have the answers.>>> >>> I was just wandering around the Sherwood site regarding receiver dynamic>> range ratings (again) and I noticed a curious thing.>>> >>> The Collins 75S-3B is rated 6 spots higher than the 75S-3C.>>> >>> Now the only difference between the two (of which I am aware) is the>> addition of the second crystal board and associated switches for added band>> coverage.>>> >>> I think maybe this tells you what the "Gauge R&R" (Readability and>> Repeatability) is for this test.>>> >>> Also, I was wondering how many samples of a given radio are tested, since>> there MUST be some degree of unit to unit variation.>>> >>> I know there are other things the drive receiver performance quality>> measurement but I find it interesting that this one test gets such high>> visibility when it can't even produce the same result from two different>> versions of the same receiver.>>> >>> Even Direct Digital SDR radios get this figure of merit rating even though>> they have no mixers! Interesting.>>> >>> Gary>>> *** You are subscribed to Collins as w5qn@xxxxxxxxxxx. If you wish to>> unsubscribe, or modify your preferences please visit>> *** >> >> *** You are subscribed to Collins as w2iy@xxxxxxxxxxx. If you wish to>> unsubscribe, or modify your preferences please visit>> ***>> >> *** You are subscribed to Collins as ars.kd6az@xxxxxxxxx. If you wish to unsubscribe, or modify your preferences please visit ***> > *** You are subscribed to Collins as brloper@xxxxxxxxx. If you wish to unsubscribe, or modify your preferences please visit ****** You are subscribed to Collins as kc9cdt@xxxxxxx. If you wish to unsubscribe, or modify your preferences please visit *** *** You are subscribed to Collins as w5qn@xxxxxxxxxxx. If you wish to unsubscribe, or modify your preferences please visit ***

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