IF for a Super Sov RP75MB - UK Vintage Radio Repair and Restoration Discussion Forum

Broomradioman · 10th Oct 2007, 10:55 am

Dear All,

I have just built a BFO so I can resolve SSB/CW on my Super Sov 75MB. Can anyone let me know the frequency of the 1st IF. Is it 470KHz or 455KHz.

cheers

Jim

Steve_P · 10th Oct 2007, 6:19 pm

It does not say in the Newnes books, but immediately before it, the RP72 and RP74 have an I.F. of 470kHz, so I would go for that. If anyone knows any different, let us know!!

Cheers,

Steve P.

G8DLG · 10th Oct 2007, 6:28 pm

The IF is 470khz + or- 2 khz (depends on the crystal filter) for the RP75,but if you are making a BFO you will be able to tune this to the IF.
The Hacker rp75 is not a good receiver for short wave anyway,better to use a proper sw receiver which would probably have a BFO.

Broomradioman · 10th Oct 2007, 9:11 pm

I do have several v good SW RXs, including a JRC 535, a 525, 3 x JST 135s

, a TS570s and a TS690s, it was just a challenge to resolve SW on the Super Sov. ( I know its like having a dog and barking yourself)

I can resolve Shanwick weather on 5505 ok and most of the calls on 5649 too, but it is very finickity to set up using the coil and the pot so I was just checking to see what the IF was. A lot of sets have a 455 IF and the output of the TenTec BFO is ostensibly 455 but I think the coil can pull it up to 470.

thanks for the guidance and comments

Jim

Station X · 10th Oct 2007, 9:25 pm

Given that you've got lots of "proper" comms receivers could you not listen for the Super Sov's local oscillator on one of them? You'll need the comms receiver's BFO switched on of course. You could then zero beat the LO with the BFO to give a direct readout of the LO frequency. On MW the LO will always operate above the frequency of the received station, so a simple calculation will give the IF frequency.

For example when receiving Arrow Rock 675 the LO will be on 1.130 MHz for a 455 KHz IF and 1.145 MHz for a 470 KHz IF.

Broomradioman · 10th Oct 2007, 9:40 pm

now why didn't I think of that?!!

Jim

Broomradioman · 13th Oct 2007, 3:22 pm

Unfortunately its an RP25A so prob not that rare!

Still it does look v nice, and goes well with its blue and black siblings

It's in a pile of radios at the mo so I'll get the serial later

Cheers

Jim

10th Oct 2007, 10:55 am	#1
Broomradioman Tetrode Join Date: Jul 2007 Location: Biggleswade, Bedfordshire, UK. Posts: 52	IF for a Super Sov RP75MB Dear All, I have just built a BFO so I can resolve SSB/CW on my Super Sov 75MB. Can anyone let me know the frequency of the 1st IF. Is it 470KHz or 455KHz. cheers Jim __________________ "not another radio?!" "Yes dear - is that another bottle of Clinique/Clarins/Dr. Hauschke?"

10th Oct 2007, 6:19 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: IF for a Super Sov RP75MB It does not say in the Newnes books, but immediately before it, the RP72 and RP74 have an I.F. of 470kHz, so I would go for that. If anyone knows any different, let us know!! Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? Last edited by Darren-UK; 17th Apr 2008 at 10:11 pm. Reason: Removed joke which caused thread to drift.

10th Oct 2007, 6:28 pm	#3
G8DLG Retired Dormant Member Join Date: Aug 2006 Location: London, UK. Posts: 48	Re: IF for a Super Sov RP75MB The IF is 470khz + or- 2 khz (depends on the crystal filter) for the RP75,but if you are making a BFO you will be able to tune this to the IF. The Hacker rp75 is not a good receiver for short wave anyway,better to use a proper sw receiver which would probably have a BFO.

10th Oct 2007, 9:11 pm	#4
Broomradioman Tetrode Join Date: Jul 2007 Location: Biggleswade, Bedfordshire, UK. Posts: 52	Re: IF for a Super Sov RP75MB I do have several v good SW RXs, including a JRC 535, a 525, 3 x JST 135s, a TS570s and a TS690s, it was just a challenge to resolve SW on the Super Sov. ( I know its like having a dog and barking yourself) I can resolve Shanwick weather on 5505 ok and most of the calls on 5649 too, but it is very finickity to set up using the coil and the pot so I was just checking to see what the IF was. A lot of sets have a 455 IF and the output of the TenTec BFO is ostensibly 455 but I think the coil can pull it up to 470. thanks for the guidance and comments Jim __________________ "not another radio?!" "Yes dear - is that another bottle of Clinique/Clarins/Dr. Hauschke?"

10th Oct 2007, 9:25 pm	#5
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: IF for a Super Sov RP75MB Given that you've got lots of "proper" comms receivers could you not listen for the Super Sov's local oscillator on one of them? You'll need the comms receiver's BFO switched on of course. You could then zero beat the LO with the BFO to give a direct readout of the LO frequency. On MW the LO will always operate above the frequency of the received station, so a simple calculation will give the IF frequency. For example when receiving Arrow Rock 675 the LO will be on 1.130 MHz for a 455 KHz IF and 1.145 MHz for a 470 KHz IF. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

10th Oct 2007, 9:40 pm	#6
Broomradioman Tetrode Join Date: Jul 2007 Location: Biggleswade, Bedfordshire, UK. Posts: 52	Re: IF for a Super Sov RP75MB now why didn't I think of that?!! Jim __________________ "not another radio?!" "Yes dear - is that another bottle of Clinique/Clarins/Dr. Hauschke?"

13th Oct 2007, 3:22 pm	#7
Broomradioman Tetrode Join Date: Jul 2007 Location: Biggleswade, Bedfordshire, UK. Posts: 52	Re: IF for a Super Sov RP75MB Unfortunately its an RP25A so prob not that rare! Still it does look v nice, and goes well with its blue and black siblings It's in a pile of radios at the mo so I'll get the serial later Cheers Jim __________________ "not another radio?!" "Yes dear - is that another bottle of Clinique/Clarins/Dr. Hauschke?"