[MRCA] SCR-610 frequency discussion

[Ray Fantini]

I have not had the pleasure of working on any of the WW2 FM sets yet. But do have a limited understanding of the technology and some small experience with fifties vintage equipment and stuff from the sixties and seventies.
The issue as I see it is that with the SCR-610 and sets like the BC-1000 or SCR-300 when they do work they are by any modern standard super wide band maybe 70 or 100 KHz wide, so wide its implacable to net with a most modern sets. The Korean War vintage radios are wide band and net well with the WW2 stuff but radios like the PRC-25 or VRC-12 are designed around 15 to 25 KHz deviation. That being said I have personally worked older sets with Vietnam era equipment at Dayton many times with no issue but when we have Joe Ham try to take part in the net with his Icom or Yahoo they have a hard time copying the stations that are so wide band being they have an IF designed around 5 KHz also there 5 KHz radios sound piss week on a set designed for wide band operation.
All that being said I would speculate that the old WW2 vintage sets are so wide band that they would not be heard or understood by any modern equipment beyond the elevation of the noise level. All modern LMRS (Land Mobil Radio Service) radios are now down to a 2.5 KHz bandwidth specification and many have gone digital to fit that requirement. Listen to the old LMRS/Public Service Allocations in low band or high band for that matter and you will be surprised by the lack of activity there today. Most of the Police and Fire operations have migrated to 800 MHz long ago.
So picking any frequency that the radios work on in the Ham band will be good, you're not going to working other Hams or DX or anything like that and with the low power and wide bandwidth of the radios not likely to create any understandable interference.
Last thought I have been doing this for a while now and have a question. Over the years I have seen several SCR-610 installations but never seen one work, I consider it a great accomplishment to see and have maybe seen only a hand full of SCR-300 that worked. Have these radios not aged well or where they that failure prone in the field? I would like to get a SCR-610 just to see if I could get it to work and how well it held up but have noticed that in the past year or two the price of everything associated with that set has gone thru the roof.  The SCR-508 appears to be a way better radio but for some reason has no following. Have to think if I had a WW2 vehicle would go with something like a TCS or SCR-245.

Ray F/KA3EKH


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From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on behalf of WW2RDO via MRCA <mrca at mailman.qth.net>
Sent: Thursday, December 28, 2017 5:27 PM
To: mrca at mailman.qth.net
Subject: [MRCA] SCR-610 frequency discussion

Here's a topic for discussion......  When setting up an SCR-610 radio net, what would be the two frequencies best used in the 2 trick pony to create an operational net.  The SCR-610 operates between 27 to 38.9 MHz FM, fone only ( 10 meter FM band ).  One frequency would obviously be 29.6 MHz FM, the Simplex frequency for 10 meter voice communications.  What about the other frequency?  In New York State, we use 29.1 MHz FM, but I understand out west, 29.4 MHz FM works better.  We're in the beginning stages of trying to set some sort of national standard here for radio operators/vehicle owners to use with this particular WW2 military radio so everybody is on the same page and can talk to one another should they choose/want to.  All comments are welcome.


Mark
WW2RDO
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