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Sony SRF M37V image problem solved
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Hi Kevin,
The Sony SRF-M37V is indeed a puzzle-- an
Ultralight with fairly decent sensitivity but barn-door selectivity, in stock
form. Allen Willie in Newfoundland has used it to receive more new TA
countries than all other Ultralight DXers combined, but for most
of us, it's just not as competitive as an SRF-T615, E100 or
DT-200VX.
During a recent visit to Oregon, I noticed the new
SRF-M37W model for sale at a Fred Meyer, so I picked up one for the Ultralight
Summertime Shootout. It looks almost identical to the SRF-M37V, but the TV
audio coverage has been replaced by weather band coverage (like the
DT-200VX and DT-400W). Price was $34.95, like the old SRF-M37V.
It hasn't been tested out yet, but if Sony improves the AM IF filter in this new
model, it would make a huge difference for us (even though it's probably wishful
thinking).
The 450 kHz IF of the model makes some decent
filter modifications possible (as you and Jim have experienced), but the E100's
1 kHz tuning steps provide a huge advantage for 9 kHz split-frequency DXing, to
chase TP's and TA's. The 455 kHz IF of the E100 also makes installation of
some VERY effective IF filters possible, such as the Murata CFJ455K5 ceramic
filter.
Your modified SRF-M37V's would make a very
interesting project for a large loopstick transplant, Kevin. We have
discovered that whenever a selectivity boost is combined with a major
sensitivity boost, an Ultralight suddenly becomes an Ultra-effective DX
chaser.
73, Gary
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dhsatyadhana <satya@...>
Hi all:
Jim Kenny and I were talking on the phone and each pulled out our M37V with a 4.5 khz retrofitted filter installed. Both of us realized that, unlike the stock M37V, there were no images from strong locals (i.e., phantom 680 signal from local 1590, etc.). I then turned on my Sony 7600GR, and the images from my strong locals were blanketing the dial, but nothing on the M37V! I even tried putting a Terk Loop up to it, and the true 680 station just came in better. So, it appears that with a decent filter, the horrid selectivity and images problems with the stock unit are done away with! Not sure if it does anything for spurs such as those that Gary DeBock finds at his QTH. I will have to check tomorrow when spur DXing conditions are at their peak :-). I am speculating that, as the TV band goes away, M37Vs will be at close- out prices pretty soon. With 5 memories and 9 khz tuning, perhaps not a bad investment! The DX challenges that remain for this little guy are working around the modest selectivity from the native micro- ferrite, and the inability to tune 1 khz off like the Eton e100 can. 73 - Kevin S Bainbridge Island, WA |
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Stephan Grossklass
--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:
Do keep in mind that the '7600GR with its wideband MW/LW frontend will be more easily overloaded by strong AM locals than a set with frontend tuning. (Its image rejection is no greater than on shortwave, i.e. an estimated 30..40 dB, for the same reason.) But in any case, improved image rejection with a better IF filter is a puzzler. Image rejection should be a function solely of the frontend, i.e. RF tuning and mixer (or, for most sets, RF tuning only, as regular mixers have no inherent image rejection). (A 680 kHz response from 1590 definitely is an image if we're looking at a single conversion set with the LO running above the tuned frequency - as it's normally the case - and an IF of 455 kHz.) Depending on achieved Q (and thus ultimately parts quality), image rejection near the bottom end of MW for sets with a single tuned IF circuit is about 30 to 50 dB. It drops quite a bit towards the high end, but as there are no strong signals directly above the band, this is not an issue. Anyway, I fail to see how the IF filter would play in here. It can't really be spurious responses either. Hmm. *scratches head* Stephan |
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huelbe_garcia@fastimap.com <huelbe_garcia@...>
Hi group,
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yesterday I was playing with Redsun RP300. It has an odd behaviour, if you tune 10-20KHz away from a string, local station, you can still listen to a demodulated and readable audio a little bit more 'trebly'. It's like a 'leakage' between the RF/AF stages. I would consider it normal if it was, say, 1-3KHz... but 20KHz is too much! On the other hand E100 works just as one expect, if you tune about 5-7 KHz (or more) away from a local station you heard the splatter, kind of noise non-readable. For a moment, I thought the filter replacement could be fix some kind of 'signal leakage'. --hg ----- Original message -----
From: "Stephan Grossklass" <sgrossklass@...> To: ultralightdx@... Date: Fri, 08 Aug 2008 10:31:52 -0000 Subject: [ultralightdx] Re: Sony SRF M37V image problem solved --- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote: Do keep in mind that the '7600GR with its wideband MW/LW frontend will be more easily overloaded by strong AM locals than a set with frontend tuning. (Its image rejection is no greater than on shortwave, i.e. an estimated 30..40 dB, for the same reason.) But in any case, improved image rejection with a better IF filter is a puzzler. Image rejection should be a function solely of the frontend, i.e. RF tuning and mixer (or, for most sets, RF tuning only, as regular mixers have no inherent image rejection). (A 680 kHz response from 1590 definitely is an image if we're looking at a single conversion set with the LO running above the tuned frequency - as it's normally the case - and an IF of 455 kHz.) Depending on achieved Q (and thus ultimately parts quality), image rejection near the bottom end of MW for sets with a single tuned IF circuit is about 30 to 50 dB. It drops quite a bit towards the high end, but as there are no strong signals directly above the band, this is not an issue. Anyway, I fail to see how the IF filter would play in here. It can't really be spurious responses either. Hmm. *scratches head* Stephan ------------------------------------ Yahoo! Groups Links |
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huelbe_garcia@fastimap.com <huelbe_garcia@...>
Sorry for the horrible english in the last message, it seems I need some
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coffee... string = strong could be fix = perhaps fixed :) --hg ----- Original message -----
From: "huelbe_garcia@..." <huelbe_garcia@...> To: ultralightdx@... Date: Fri, 08 Aug 2008 11:29:22 -0300 Subject: Re: [ultralightdx] Re: Sony SRF M37V image problem solved Hi group, yesterday I was playing with Redsun RP300. It has an odd behaviour, if you tune 10-20KHz away from a string, local station, you can still listen to a demodulated and readable audio a little bit more 'trebly'. It's like a 'leakage' between the RF/AF stages. I would consider it normal if it was, say, 1-3KHz... but 20KHz is too much! On the other hand E100 works just as one expect, if you tune about 5-7 KHz (or more) away from a local station you heard the splatter, kind of noise non-readable. For a moment, I thought the filter replacement could be fix some kind of 'signal leakage'. --hg ----- Original message ----- From: "Stephan Grossklass" <sgrossklass@...> To: ultralightdx@... Date: Fri, 08 Aug 2008 10:31:52 -0000 Subject: [ultralightdx] Re: Sony SRF M37V image problem solved --- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote: Do keep in mind that the '7600GR with its wideband MW/LW frontend will be more easily overloaded by strong AM locals than a set with frontend tuning. (Its image rejection is no greater than on shortwave, i.e. an estimated 30..40 dB, for the same reason.) But in any case, improved image rejection with a better IF filter is a puzzler. Image rejection should be a function solely of the frontend, i.e. RF tuning and mixer (or, for most sets, RF tuning only, as regular mixers have no inherent image rejection). (A 680 kHz response from 1590 definitely is an image if we're looking at a single conversion set with the LO running above the tuned frequency - as it's normally the case - and an IF of 455 kHz.) Depending on achieved Q (and thus ultimately parts quality), image rejection near the bottom end of MW for sets with a single tuned IF circuit is about 30 to 50 dB. It drops quite a bit towards the high end, but as there are no strong signals directly above the band, this is not an issue. Anyway, I fail to see how the IF filter would play in here. It can't really be spurious responses either. Hmm. *scratches head* Stephan ------------------------------------ Yahoo! Groups Links ------------------------------------ Yahoo! Groups Links |
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