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New detector and AGC for the RME-45B




 
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Author Topic: New detector and AGC for the RME-45B  (Read 461 times)
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G8VOQ
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« on: November 07, 2018, 06:33:53 AM »

Hi. Just recently bought an RME-45B. I understand that stock performance will be pretty mediocre. I'm looking at improving performance by substituting the am detector and AGC system by a better arrangement. Specifically, I have in mind a low distortion AM detector and AGC system by Steve Cloutier WA1QIX. If I use this, I think I have no option but to self-build.

Although, I wish I could just purchase a new am detector and agc system and fit it to my RME-45B.
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G8VOQ
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« Reply #1 on: November 11, 2018, 07:51:43 AM »

Hi. In my initial post, I added the last sentence in the hope that if someone had managed to purchase a ready-made AM detector product or perhaps a kit of parts, someone might pipe up and reveal that. :-)

I have not searched much, but only product I know of that you can buy is the Sherwood SE3, which is very expensive, but seems really good.

Could AMfone think of offering AM detector and AGC kits for purchase? Or anbody for that matter?  Could there be a product made to compete (pricewise) with Sherwoods SE3? (Technically of course yes, but that takes some enteprenuerial and technical effort).

Posting in not as such about Sherwoods SE3, But nice discussion here about that product:

http://amfone.net/Amforum/index.php?topic=18357.0
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Patrick J. / KD5OEI
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« Reply #2 on: November 11, 2018, 11:41:27 AM »

Too bad Sherwood stopped making them. An SDR or other kind of digital monster could be made to do that but the Sherwood is all analog.

Did you want a simple low distortion detector or a full synchronous detector? There are lots of articles on both, even with vacuum tubes. There is one particular kind of simple op-amp based envelope detector that is supposed to be very clean. It's been discussed here before but I don't know where.

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Radio Candelstein - Flagship Station of the NRK Radio Network.
MikeKE0ZUinkcmo
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« Reply #3 on: November 11, 2018, 11:21:37 PM »

I built Steve's detector and AGC system a few years ago and installed it into a National HRO-60.   It worked VERY well.   I recently purchased an HRO-50 and am thinking about installing another copy in this radio as well.
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Mike KE0ZU

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G8VOQ
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« Reply #4 on: November 12, 2018, 05:56:59 AM »

The way I see it, we are let down somewhat in our hobby, by our receiver's ill designed, or poor performing AM detector circuits.  That our enjoyment would be enhanced when we can obtain intelligability of signals even during deep fading episodes and even when the signal is just above the noise.

Sure, we can, on an individual basis, procure a solution by homebrewing our own detector design, or building someone elses design, or purchasing a commercial product (at great expense in some cases).

So, the thought occurs, would it be possible for some members of AMfone to get together to develop or offer a detector solution.  Sold on a commercial basis, however, primarily not with an intention to reap significant profits but sort of provide an afforable and convenient service.

Perhaps the offer could be synchronous and non synchronous detection.

Perhaps profits could sustain AMfone.

Personally, I'm not keen on needing to use a PC as a solution.

EDIT: I get my RME-45B today. Can't wait.  Smiley
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Patrick J. / KD5OEI
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« Reply #5 on: November 13, 2018, 10:27:37 AM »

The advantages of SDR and computer integration in a station are many, but not having to rely on digital black boxes for useful and enjoyable radio activity is a strategic advantage and not to be pooh-pooh'd. Besides, it's fun.

Do you have the manufacturing files?

What about the SE-3? If it's no longer made, would Sherwood engineering allow others to make the unit from the schematic or even release the gerbers? just a consideration about that.

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Radio Candelstein - Flagship Station of the NRK Radio Network.
PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #6 on: November 13, 2018, 01:12:36 PM »

I moved into a new house here in Costa Rica, and my shack isn't ready yet, will take an other month or so. I am planning already quite some time to make a general purpose sync detector / AVC generator for several radios I have here based at the 4046 PLL. No fancy IC's made of inobtanium, just a few transistors / fets and CMOS series 4000 IC's. I will keep you informed about the progress, but it has to wait for the shack to start. The build will be dead bug in first instance, perhaps later a PCB
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WBear2GCR
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Brrrr- it's cold in the shack! Fire up the BIG RIG


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« Reply #7 on: November 13, 2018, 04:30:50 PM »

Heresy says buy a dongle that runs down the to IF frequency, take it off the 1st mixer or 1st IF and run that
into an SDR dongle. All done in one shot. The receiver becomes a very good preselector... Cheesy

Also, I think the dongle wants no AGC as its input...
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_-_- bear WB2GCR                   http://www.bearlabs.com
kb4qaa
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« Reply #8 on: November 13, 2018, 05:29:05 PM »

The Sherwood SE-3 has been out of production for several years.

Here is a synchronous detector project from QST:

JUL 1993 - QST (PG. 28)
Synchronous Detector for AM Transmissions, A
Author: Vermasvuori, Jukka, OH2GF
Article: QST Archive [PDF]
Keywords: SYNCHRONOUS DETECTOR AM TRANSMITTER CONSTRUCTION HOMEBREW

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w8khk
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« Reply #9 on: November 13, 2018, 05:37:12 PM »

One of our own, Bill Nagle W3DUQ (SK) published his in 73 and it may be found here: 
https://www.americanradiohistory.com/Archive-DX/73-magazine/73-magazine-1967/73-magazine-09-september-1967.pdf

And Steve compiled quite a compendium on synchronous detection on THIS forum... http://amfone.net/Amforum/index.php?;topic=18379.0
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Rick / W8KHK  ex WB2HKX, WB4GNR
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Patrick J. / KD5OEI
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« Reply #10 on: November 14, 2018, 12:44:46 AM »

some more

Surrey Electronics AM synchronous detector manual 1988
GE Ham News Vol 03 No 6
GE Ham News Vol 06 No 4
Popular Electronics April 1982

haha well so much for detectors, are there more to study?

But the OP was about 'detection' and AGC, so what articles might there be on lowest distortion envelope detectors, and how to get AGC voltages and use them?

There are a lot of other good receivers that have no AGC, like the Rycom R1307A. Applying AGC may be more complicated add-on due to differences between sets and some sets not having reasonable RF or IF gain controls.

There is this AGC but it's op-amps, not sure how it might apply to the original post.
KA9NEH, Fred Baumgartner., 73 mag SEP 1990
https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/73/1990/09/page32/index.html
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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