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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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9th Nov 2020, 5:30 pm | #1 |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 319
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SSM Sentinel 2m to MW converter
I recently retrieved this converter from a box at the back of the shed (where else?) but have since drawn a complete blank on the internet when searching for a circuit or any other technical details. I had the same problem with the SSM 28-144 QRO transverter a while ago but, needless to say, someone on this list came up with full technical spec. and a circuit.
The 'Sentinel MF' converter was designed largely for /M back in the amplitude modulated days of 2-metre mobile. It is specifically intended for tuning on a MW car radio 0.5-1.5 MHz (600-200 m) and has two separate local oscillators for inputs in two switched bands 144-145 and 145-146. A 1974 SWM advertised it for this purpose at a price of £20.25. I have a PCR receiver with added BFO and this little converter should work well with it. Has anyone out there got any further details? I'll bet that someone does . . . Peter G3PIJ |
9th Nov 2020, 6:39 pm | #2 |
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Re: SSM Sentinel 2m to MW converter
Sentinel were based in Huddersfield. Longley, I think. Out of my price range at the time so I've no other knowledge of them even though I lived a few miles away.
David
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10th Nov 2020, 12:43 am | #3 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
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Re: SSM Sentinel 2m to MW converter
What a thing! I vaguely remember them being advertised.
I wonder what the image rejection was? ~Zero? I should think they bothered with 2 crystals only so the tuning worked in the right direction. |
10th Nov 2020, 1:02 am | #4 |
Dekatron
Join Date: Apr 2009
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Re: SSM Sentinel 2m to MW converter
I recall SSM being very popular for some period of time. However, I also seem to recall that they used 40673 mosfets at the front and failure was rather common-place.
B
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10th Nov 2020, 2:31 am | #5 |
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Re: SSM Sentinel 2m to MW converter
Two crystals make it look like a double conversion converter. One way to ease the image rejection problem.
David
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10th Nov 2020, 11:27 am | #6 |
Nonode
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Location: Welwyn Garden City, Hertfordshire, UK.
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Re: SSM Sentinel 2m to MW converter
Wouldn't that need 3 crystals to get 2x Switched Bands it clearly supports?
Both oscillators look identical apart from minor layout changes. I'm with single conversion. |
10th Nov 2020, 11:33 am | #7 | |
Hexode
Join Date: Nov 2011
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Re: SSM Sentinel 2m to MW converter
Quote:
The converter does not seem to have been 'got at' and is in a physically clean condition so I suppose the time has now come for 'suck it and see' - plug it in, see what happens and take it from there. One thought on the circuit is that it might just be the same as that fitted in the Europa TX/RX transverter - for which I have all docs. Peter |
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10th Nov 2020, 12:18 pm | #8 |
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Re: SSM Sentinel 2m to MW converter
OK, so single conversion, two bands set by two LO frequency choices.
There can be very little image suppression, but back then the band wasn't much populated David
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10th Nov 2020, 1:59 pm | #9 | |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
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Re: SSM Sentinel 2m to MW converter
Quote:
As usual, the image frequency is 2 x IF away from the desired frequency. Additive mixing does not come into the picture with these frequencies. The image response is set by the Q of the pre-mixer tuned circuits. It looks like there are two of these associated with the RF amp. Good enough to distinguish between two signals around 150 MHz that are 2 MHz apart? Not sure! Peter G3PIJ |
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10th Nov 2020, 3:51 pm | #10 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
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Re: SSM Sentinel 2m to MW converter
There was a version published in USA which by choice of crystal put the Club Net and the Calling Frequency on each side at the same IF tuning.
The idea presumably being you had twice the chance of hearing something, anything, please! |
10th Nov 2020, 10:49 pm | #11 | |
Hexode
Join Date: Nov 2011
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Re: SSM Sentinel 2m to MW converter
Quote:
Peter G3PIJ |
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12th Nov 2020, 2:20 am | #12 |
Dekatron
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Re: SSM Sentinel 2m to MW converter
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12th Nov 2020, 6:56 pm | #13 |
Hexode
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Re: SSM Sentinel 2m to MW converter
Looking at the photos of yours and mine, it seems to me that the physical layout of the RF amplifier sections are almost identical - but that's where the similarity ends. The two PCBs are different animals. I expect that any firm of this sort back then would repeat what works and adapt / develop the rest to suit the specific need. When I've got a spare five minutes, I'll plug in my MW BC RX version and see what happens!
Peter G3PIJ |
16th Nov 2020, 5:33 pm | #14 |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
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Re: SSM Sentinel 2m to MW converter
Well - surprise, surprise! I attached the converter to the much-modified PCR set (BFO plus internal AC PSU) and to a Marconi TF2008 signal generator. After replacing the wire from the mixer output to the selector switch that someone in their wisdom had removed, the thing burst into life. Ultimate sensitivity looks to be around 0.2 microvolts and tuning the 2-metre band in two bites across the whole of the medium waveband gives almost ridiculous bandspread.
Time to reassemble the J-Beam 5-over-5. I also have an SSM Europa 28-144 transverter with a dead RX side somewhere or other . . . who knows where this project will end? Peter G3PIJ |
16th Nov 2020, 5:38 pm | #15 |
Dekatron
Join Date: Apr 2012
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Re: SSM Sentinel 2m to MW converter
At least with your modified PCR you've got a BFO, so SSB and CW stations (and slope-detected FM) will be resolvable.
AM on 'two' is really rather uncommon these days, I think it was about 15 years ago I last heard it used. "Tuning low to high"..... |
16th Nov 2020, 7:11 pm | #16 | |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
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Re: SSM Sentinel 2m to MW converter
Quote:
There is a modicum of activity around here on FM. This SSM MW converter will allow me to check around 144300 for SSB activity to be sure it will be worth while firing up the SSM Europa transverter. I also have a well-built GW3ZTH transverter using a QQVO3-10 balanced mixer into a QQVO6-40A - see SWM March 1973 pp. 29-33 at https://worldradiohistory.com/UK/Sho...WM-1973-03.pdf When last used around 20 years ago, there was precious little activity and so it fell into disuse. Possibly time for another outing? Or not? Peter G3PIJ |
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16th Nov 2020, 7:36 pm | #17 |
Heptode
Join Date: Mar 2008
Location: Newmarket, Suffolk, UK.
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Re: SSM Sentinel 2m to MW converter
RSGB organise an Activity Contest every month on the 1st Tuesday
FM 7 to 7 55pm then Largely SSB 8 to 10.30pm local There is also an activity group who use SSB on 144 265 Not that I do either 73 Fred G4BWP |
16th Nov 2020, 7:44 pm | #18 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: SSM Sentinel 2m to MW converter
There was a ramping-up of 2M activity round here [and also reported happening in other parts of the UK] when the first lockdown began - people dusting off their old radios and getting back on-air. It's tailed-off a bit since though: 2M activity has been in notable decline ever since us Class-B [I always think that sounds like we operate in zero-bias push-pull!] types got full HF privileges a couple of decades back.
There was some "vertically polarised SSB" activity on 144.250 a while back, with people using 'white stick' type collinear omnidirectional antennas. This was criticised in some circles but I'd rather have omnidirectionally-squirted signals on a bit of the band than the usual deafening silence. For winter I'm looking at firing up one of my Pye Westminsters again. |
16th Nov 2020, 8:48 pm | #19 |
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Re: SSM Sentinel 2m to MW converter
My memory has just popped up an address
SSM Solid State Modules Dalton Green Lane, Dalton, Huddersfield. I think I said Longley in error earlier. A bit of searching turned up number 14. It's probably changed hands a few times since. Despite living about a mile away, I never met the chap. David
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16th Nov 2020, 8:56 pm | #20 |
Hexode
Join Date: Mar 2006
Location: Helston, Cornwall, UK.
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Re: SSM Sentinel 2m to MW converter
There is a lot more activity on the V/UHF bands over the last couple of years, not so much on FM but quite a lot on SSB and the data modes which have shown what is actually possible on the bands. Paths of over 4000 kms are regularly worked on 2 and 70 from the U.K. and Eire, Regular transatlantic QSO’s from Cape Verdi (D4) to The Caribbean.
It’s only a matter of time before the Brendan trophy is claimed for the first trans Atlantic QSO from Europe to the US takes place. Very interesting times |