Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Collins purchase question  (Read 915 times)
WB8PFZ
Member

Posts: 290




Ignore
« on: May 18, 2019, 12:55:30 PM »

I am thinking of selling a few radios and purchasing a Collins setup. Is there a Collins radios for dummy book that will tell me the ins and outs of what to buy or not to buy? Thanks Mike
Logged
N4UE
Member

Posts: 867




Ignore
« Reply #1 on: May 18, 2019, 01:50:24 PM »

Hi Mike. I'm no Collins 'expert' even though I have a few.
Join the Collins Collector Association. Great guys.

What vintage are you interested in?

Gold Dust Twins....75A-4/KWS-1
S-Line
HF-380

The S-Line was typically built for the Military. The transceivers are not the best for CW (I've been told).
You might be best served by the 75S-3(B/C) receiver and the matching transmitter.

Even if you're not up to working on them, there are some GREAT guys out there, that can handle any issue.
Look at the reviews here. I've used K2LRC for a PTO that I messed up, and his work was flawless.

ron
N4UE
Logged

If you're not the lead sled dog, the view never changes......
WB8PFZ
Member

Posts: 290




Ignore
« Reply #2 on: May 18, 2019, 05:01:06 PM »

Thinking about an S line. I wasn't sure about the difference between a B and a C but it appears they are the same with a few minor differences. Had a 75A1 back in 73. What a boat. Mike
Logged
VK6HP
Member

Posts: 455




Ignore
« Reply #3 on: May 19, 2019, 08:15:57 PM »

Mike

I would endorse Ron's suggestion re the CCA.  At the very least, check out the Web site - it contains a wealth of information relating to Collins gear of all vintages.

If you plan to do any CW with an S-line station there's really only one transmitter option that works, namely a 32S-3.  Other transmitter and transceiver options involve audio tone keying and, with only small misadjustment or drift, produce spurious output levels inconsistent with contemporary expectations.  The 32S-3 does "proper" CW.  

The matching 75S-3 receiver is a natural twin to use with the 32S-3 transmitter.  I have a 32S-3 and a 75S-3B and much enjoy the flexibility that the variable BFO (in addition to the crystal BFO) gives on SSB and CW when the twins are used in transceive mode.  The S-line units all produce superlative SSB and the 32S-3 does excellent CW.  It is still the cleanest exciter around and I've used mine to test even contemporary LDMOS amplifiers.

I also have a 30L-1 linear amplifier which, while not without quirks, works very well on all bands.

Many details of the more subtle model variations (including A/B/C variants) can be gleaned from the CCA site and, in particular, from the "Signal" magazine, back issues of which also available to download.  Good luck, and keep us up to date with your selection.  (You can see my gear on my QRZ page; my tiny shack, plus a philosophy of regularly using all the classic gear, limits my hoarding tendencies).

73, Peter.
« Last Edit: May 19, 2019, 08:22:34 PM by VK6HP » Logged
WB8PFZ
Member

Posts: 290




Ignore
« Reply #4 on: June 12, 2019, 08:39:39 AM »

I see some 75S3B receivers with the crystals installed on the left side of the radio. Some do not have any. How does the receiver operate without the crystals? Mike
Logged
W1BR
Member

Posts: 4147




Ignore
« Reply #5 on: June 12, 2019, 09:01:33 AM »

They use the crystals installed in the mating 32Sx transmitter.  For standalone, or for use with a non-compatible transmitter, you would need the crystals. 
Pete
Logged
WB8PFZ
Member

Posts: 290




Ignore
« Reply #6 on: June 12, 2019, 11:41:02 AM »

That was my guess unlike Heathkit that has the crystals in the receiver. Thanks Mike
Logged
W1BR
Member

Posts: 4147




Ignore
« Reply #7 on: June 12, 2019, 12:38:00 PM »

I meant to say they used the crystals in the receiver... typed to fast. 
Logged
WB8PFZ
Member

Posts: 290




Ignore
« Reply #8 on: June 12, 2019, 12:41:02 PM »

Ok, it seems I have seen a pack of crystals on the bottom of the receiver. Is that possible? Mike
Logged
VK6HP
Member

Posts: 455




Ignore
« Reply #9 on: June 12, 2019, 05:24:11 PM »

Mike,

Yes, the crystal arrangement you describe is standard on a 75S-3C and is often used on other S-line variants, as described on the CCA site.  The thing you're probably missing is the small, 2 position rotary switch above the front panel band switch.  It switches between two crystal decks, with the "main" or ham band deck being under the chassis.  The top deck gives another 14 crystal positions, which are often populated with WARC, or any other desired HF bands (amateur or other). When the small switch is rotated, another band marking card which, like the primary one can also be filled in by the user, flips into position beside the band switch knob pointer.


Peter.
« Last Edit: June 12, 2019, 05:29:03 PM by VK6HP » Logged
WB8PFZ
Member

Posts: 290




Ignore
« Reply #10 on: June 13, 2019, 04:40:56 AM »

Thanks Mike
Logged
AD4U
Member

Posts: 2537




Ignore
« Reply #11 on: June 14, 2019, 06:10:12 AM »

When I got into HAM radio in the 1960's, I could only drool at Collins gear. Finally in 2015 I started buying some Collins gear. My Collins 75S3 and 75S3C are fine receivers even by today's standards My Collins 32S3 transmitter paired with either the 75S3 or the 75S3C is great on SSB or CW. My Collins KWM2A (round emblem) is a great SSB rig but a poor CW rig. The KWM2(A) generates a 1750 Hz audio tone on the carrier to send CW. What was Collins thinking when they did this. 

The 75S3C and the KWM2A has the aux crystal board that allows the rigs to operate on must about any frequency between 3.4-30 MHz. This is great for WARC bands etc.  I bought the Collins CP1 crystal pack that has ALL crystals that can be installed for operation on 3.4-30 MHz.

Dick AD4U

Logged
K4PF
Member

Posts: 14




Ignore
« Reply #12 on: June 14, 2019, 10:32:20 AM »

AD4U noted -
The KWM2(A) generates a 1750 Hz audio tone on the carrier to send CW. What was Collins thinking when they did this? 

Hi,

The reason for the high audio sidetone, which is also results in a high c.w. offset from the carrier
frequency, is to avoid transmitting the second harmonic of the audio tone.  If they had used a 1 KHz
tone, the second harmonic (2 KHz) would also appear in the transmitter's output, as a second
keyed signal offset 1 KHz up from the main signal. The audio passband is from about 300 Hz
thru 2400 Hz, using the stock 2.1 KHz bandwidth mechanical filter, thus there would be no rejection
of that 2 KHz audio distortion product.

The audio generator in the KWM-2 is a simple phase shift oscillator, so its second harmonic may be
only 30 dB down or so.  If that were transmitted along with the "main" c.w. keyed tone, it would
be a significant spur when using c.w. mode.  By using a 1750 Hz sidetone, the rf signal caused by
the second harmonic of the audio oscillator (3500 Hz) is well down on the slope
of the mechanical filter passband, so it is adequately attenuated.

The KWM-2 c.w. system does work, you just need to get used to copying the received c.w. signal
at a 1750 Hz pitch in order to maintain zero beat.  An audio filter that can be peaked at 1750 Hz
in the received audio chain would help - something like the old National Select-O-Ject.

I only know of one ham who regularly uses his KWM-2 on c.w.

73, Ed
Logged
K4PF
Member

Posts: 14




Ignore
« Reply #13 on: June 16, 2019, 10:58:55 AM »

Operating the KWM-2 on c.w. is well-discussed here:
https://archive.org/stream/73-magazine-1964-11/11_November_1964#page/n45/mode/1up

The article also discusses the use of a Heathkit Q-multiplier to get receive c.w, selectivity with the KWM-2.

The 73 author noted that his sidetone was 1.5 KHz.  I've seen specs like 1350 Hz or 1450 Hz as well,
but haven't seen 1750 Hz discussed before.

73, Ed
Logged
VK6HP
Member

Posts: 455




Ignore
« Reply #14 on: June 16, 2019, 05:54:31 PM »

The audio oscillator tone crept up in frequency with production era as the problems with CW operation, especially in poorly adjusted transceivers (including those with less-than-optimum opposite sideband suppression), surfaced.  A very good overview of the transmit conversion chain, and a modern modification for CW operation is given in a relatively recent article by WB2ZKW:

http://www.arrl.org/files/file/QST%2520Binaries/KWM2%20on%20CW.pdf

This is a good solution but I would probably never implement it in my classic Collins transceiver!

It's a personal preference but if I were starting a Collins S-line collection from scratch I'd look for a good transmitter/receiver combination, for the reasons we've been discussing and because the twins are somewhat easier to maintain for a Collins novice.  You really want to be using your classic gear regularly, both for its benefit and yours, and you'll find that the tx/rx boxes are easier to work on. Again personally, I think you also end up with a better result and a few worthwhile operational advantages, such as (in my case) the ability to use the variable BFO on the 75S-3B as an RIT.  

Having said that, I've just spent quite a lot of time repairing and bringing a friend's KWM-2A up to specification, and it's a great radio too. What you end up with may come down to the opportunities presented to you, and the quality of the radios on offer.  There are good specimens out there, but there are plenty of partly trashed and poorly modified units as well.

73, Peter.
« Last Edit: June 16, 2019, 06:14:42 PM by VK6HP » Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!