WA1GFZ
Member
 Offline
Posts: 11151
|
 |
« Reply #25 on: January 06, 2009, 08:22:20 AM » |
|
The 1N60s near the AGC diodes are the AM detector
|
|
|
|
|
Logged
|
|
|
|
WD8BIL
Contributing
Member
Offline
Posts: 4400
|
|
« Reply #26 on: January 06, 2009, 08:30:49 AM » |
|
G,
If needed I have 1n914s and 1n4148s. I know Jay has offered so consider me a second source.
Jay: Yes indeed. I hope we hear the band in that kinda shape often this winter!
You strapped!!
|
|
|
|
|
Logged
|
|
|
|
W2INR
Radio Syracuse
Founding
Member
Offline
Posts: 1149
Syracuse Radio W2INR
|
|
« Reply #27 on: January 06, 2009, 10:08:20 AM » |
|
Thanks Jay on the diodes , what is FCM?
T, I have the AM/FM board so I did the DUQ mods. It works great.
Frank, if I wanted to change out the AM detector what could I use there that may be better?
TNX Buddly
G
|
|
|
|
|
Logged
|
G - The INR
Amateur Weather Station KNYSYRAC64
Creator - owner - AMfone.net - 2001 - 2010
Founding Member - NEAR-Fest
SWLR-RNŲ54
|
|
|
|
Steve - WB3HUZ
Guest
|
|
« Reply #28 on: January 06, 2009, 10:37:12 AM » |
|
Just take the 455 IF out to your downconvertor and use the Flex sw.
|
|
|
|
|
Logged
|
|
|
|
W2INR
Radio Syracuse
Founding
Member
Offline
Posts: 1149
Syracuse Radio W2INR
|
|
« Reply #29 on: January 06, 2009, 11:00:59 AM » |
|
Not enough signal Steve, doesn't work off of the jack in the back
But that does pose another question. Where would be a good pick off point for a 455 signal to the Soft rock IF board?
G
|
|
|
|
|
Logged
|
G - The INR
Amateur Weather Station KNYSYRAC64
Creator - owner - AMfone.net - 2001 - 2010
Founding Member - NEAR-Fest
SWLR-RNŲ54
|
|
|
WA1GFZ
Member
Offline
Posts: 11151
|
|
« Reply #30 on: January 06, 2009, 11:30:06 AM » |
|
A source follower FET stage would allow you to pick it off any place.
I would think around Q11 would be a good spot.
1N60 is a 1N34s little brother. I would think a 914 or 4148 would work fine and have much better leakage. The 5711 will work down to a lower level but you have plenty of signal at Q11. When I did my homebrew RX I found the active detector worked the best and K2CU improved on the one I pulled out of RF design years ago. Softrock is a great spectrum monitor as well as demodulator. gfz
|
|
|
|
|
Logged
|
|
|
|
W1VD
Contributing
Member
Offline
Posts: 401
|
|
« Reply #31 on: January 06, 2009, 11:53:36 AM » |
|
FCM = First Class Mail
Used the K2CU demod on the R-390A before switching to the softrock setup and it worked well. Been meaning to do the AM audio recovery measurements on it to see just how good it is. May get a chance later in the week...been curious for a while now. A Drake 2C is ready for the torture rack tonight.
|
|
|
|
|
Logged
|
'Tnx Fer the Dope OM'.
|
|
|
W2INR
Radio Syracuse
Founding
Member
Offline
Posts: 1149
Syracuse Radio W2INR
|
|
« Reply #32 on: January 07, 2009, 09:41:01 AM » |
|
FB on the source follower. I am going to try that once everything else is set.
TNX
G
|
|
|
|
|
Logged
|
G - The INR
Amateur Weather Station KNYSYRAC64
Creator - owner - AMfone.net - 2001 - 2010
Founding Member - NEAR-Fest
SWLR-RNŲ54
|
|
|
WA1GFZ
Member
Offline
Posts: 11151
|
|
« Reply #33 on: January 07, 2009, 10:07:46 AM » |
|
The softrock is quite sensitive but low Z input so it must be sucking the signal down. Good FETs to use 2n4416, U308, U309, U310
|
|
|
|
|
Logged
|
|
|
|
WA1GFZ
Member
Offline
Posts: 11151
|
|
« Reply #34 on: January 07, 2009, 12:58:56 PM » |
|
Ya Know, 1N5711s are like gold to me. Maybe better to try cheap switching diodes to see if you really found the source of the problem. If they work ok leave them. Then save the 5711s for a place that needs them. Just a thought...
|
|
|
|
|
Logged
|
|
|
|
Jim KF2SY
Member
Offline
Posts: 290
|
|
« Reply #35 on: January 08, 2009, 09:19:59 PM » |
|
Gary,
Measuring those various flavors of Ge diodes on a regular ohm meter (depending on setting) can give you fits.
They will all measure leaky (reverse) by nature (compared to a silicon). Unless they are physically cracked, they are usually ok. Betcha its a shorted e'lytic cap sucking down IIRC ? Q11 or Q12.
My 2 cents
G/L
Jim
|
|
|
|
|
Logged
|
|
|
|
K4TLJ
Member
Offline
Posts: 77
|
|
« Reply #36 on: January 09, 2009, 12:13:50 AM » |
|
Frank, if I wanted to change out the AM detector what could I use there that may be better?
TNX Buddly
G
I am not Frank but you might consider this circuit that I used in a Heathkit. It greatly improved AM detection. |
|
|
|
Logged
|
Regards
Terry
K4TLJ
|
|
|
W2INR
Radio Syracuse
Founding
Member
Offline
Posts: 1149
Syracuse Radio W2INR
|
|
« Reply #37 on: January 10, 2009, 05:05:58 PM » |
|
UPDATE:
The diodes Jay sent me arrived today and I replaced the suspect diodes. It turned out 2 of the four diodes I replaced on the IF board had no readings either way in the diode mode on my Fluke DVM. The other two read fine.
What I find interesting is one diode in each circuit was bad. One in the AM detector and one in the AGC rectifier.
Next are the product detector mods.
Terry, thanks for the AGC circuit. At this point I am going to keep the circuits as stock as possible.
Thanks to all for all the help,the radio sounds much better now.
G
|
|
|
|
|
Logged
|
G - The INR
Amateur Weather Station KNYSYRAC64
Creator - owner - AMfone.net - 2001 - 2010
Founding Member - NEAR-Fest
SWLR-RNŲ54
|
|
|
WA1GFZ
Member
Offline
Posts: 11151
|
|
« Reply #38 on: January 10, 2009, 08:18:18 PM » |
|
Bud,
When I built my last homebrew RX I went through all of them and settled on the wide dynamic range detector I got out of RF design. K2CU threw it into his simulator and came up with an even better one. I would use Rob's circuit if I was to do it again. Note at 455 KHz the layout and op amp selection more critical than 50 KHz.
Gary, Glad you fixed the AGC. Good thing it wasn't a leaky cap which would have been a pain. Sounds like you need a bag of 1N5711s. I actually figured one diode was open because you didn't have enough AGC action but some.
No action I would have suspected a shorted diode.
|
|
|
|
|
Logged
|
|
|
|
|
