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I got another LM386 audio amplifier and made some measurements. I measured with the 10ufd cap between pins 1 and 8 and with pins 1 and 8 open. With pins 1 and 8 open (minumum gain) I measured 26db. With the 10ufd cap between pins 1 and 8 (maximum gain ) I measured 46db. Both min and max gain measurements were identical to the spec sheet.
I kept wondering why the spec sheet was saying gains of 20db minimum to 200db maximum. As it turns out, they weren't saying this. The were saying gains of 20 and 200 (ratio of output voltage/input voltage). Expressed in db (20 * log V1/V2) this comes out to 26db and 46db respectively. How I came up with 68db in a previous post is beyond me.
The moral of this is - don't believe everything you read - particularly when it comes from me .  My apologies.

I hope to make more measurements like MDs, blocking dynamic range and two tone dynamic range tests in the near future. I will try and outline my test procedures so that if someone sees any glaring errors, they will tell me. This will be a first for me.

Tom, ak2b

C'mon Leonard, the little LM386 Amplifier Kit takes 15 minutes to assemble. You can't tell me that you are not tempted to put together at least one of your 12 kits. I timed myself today and built the Gilbert Cell audio detector in 76 minutes. The diode ring mixer took a little longer. I figured I'd build up some boards and test them individually since on the first go around I was too impatient to get something working. Also, I can do different things with different boards and just swap them out.

I like to build and after building every kit available (or at least it seems) I got tired of just stuffing parts onto a board. The only time I would learn anything is when it didn’t work. These little boards are a lot of fun and easy to modify and I’ve learned a great deal in the process of building my transceiver.

In any case, thanks for your nice comments and I hope it doesn’t take years before you get back into building. Your web page on Double Balanced Mixers and screen shots from your spectrum analyzer are excellent and are better than any text book I've ever seen in explaining what happens with a DBM.

Although I would like to be, I am not retired and still work. I am not married and live in a city apartment so come Saturday morning there is no need to mow the lawn or mend the fences. I just make some coffee and head for the shop – which in my case is the dining room table - about a foot from where the coffee is made.

Tom, ak2b

I spent the weekend trying to do some meaniful measurements with my Erector RX. This turned out to be more difficult than I anticipated. I used this document from the ARRL to run the tests:
http://www.arrl.org/members-only/prodrev/testproc.pdf
This is not the latest versions of the ARRL's test procedures but for my purposes it is good enough.

I am so unsure of the results that I'm not going to post them until I get a little bit more confident in my procedures. I have a K2 and plan to test both radios one after another. At least with the K2 I know around where I should be measuring.

Tom, ak2b

The two step attenuators and the HP8640B I bought on eBay. I paid about $100 each for the attenuators and about $300 for the HP8640B. The Mini-Circuits ZFSC-2-6 http://www.minicircuits.com/pdfs/ZFSC-2-6.pdf was $50 direct from Mini-Circuits. After collecting all this over a period of time this is the first serious testing I have done with all of it together.
I quickly tried a BDR test on both units last night and came to the conclusion that quick tests aren't the way to go. The Erector RX looked better than the K2 by quite a lot. I know this can't be right.
The test procedures described by the ARRL left me a little confused. I will try again.

Tom, ak2b

Hi leonard,
I've gotten the best bargains on eBay just about Christmas time when people have their minds on other things. The HP8640B is a great instrument if you happen to get one in decent shape. I took a chance and bought mine without warranties and no proof of calibration. The XG2 is also quite handy since it puts out a pretty accurate low level signal at 1uv (-107dbm). One of the handiest pieces of test equipment I own is the FPM-1 power meter/frequency counter from m3electronix http://www.m3electronix.com/features1.html I also bought the RF Calibrator from them. It claims to measure RF down to -72dbm.  I put it up there in usefulness with my AADE L/C meter - you can live without it, but I'd rather not.
Talk about having enough time, I looked at your manual and other things you've done with the Bitx20. That's a lot of work, Leonard .

Tom, ak2b

One row of the BPF's, LPF's and pin diode switch boards are mounted on the back of the transceiver. The pin diode switch between the low pass and band pass filters, I realized after I mounted it, is not needed since it is duplicated on the transmitter board. I rewired the transmitter board according to the schematic to accommodate using the LPF for both transmit and receive. Actually, I could probably also use a pin diode switch on the output of the DDS VFO to switch between the TX and RX frequency and do away with the splitter and attenuator entirely. The switch on the left below the meter position will handle the TX/RX voltages for three bands so I'm adding 15 meters to my original 20M/17M transceiver. I should be finished by this weekend and will report further.
Sometimes I feel like the dumbest person on earth. Forever I thought that the labels XMIT+8 and RCVE+8 at J1 on the linear amp meant the signal lines plus 8 volts. This threw me off for the longest time until I saw the pin diode switches with the same labels. Finally it dawned on me that this lines were simply 8V TX and 8V RX. Oh well, it's not the first time I've been so stupid, when I was first licensed in the early 60's, for years I thought SKN was Silent Key Night .

Tom, ak2b

Last edited by ak2b (2009-04-19 09:12:27)

After poking around  Q1 on the Linear Amplifier the TX 8 volt line (J1 pin 1) went to 0 volts while in receive and everything sounds fine. Why the problem went away, *I don't have a clue. It doesn't appear to be intermittant - just a solid 0 volts while in receive. The downside to all this is the power dropped down to 1.5W .
Oh well, time for a little trouble shooting.

Tom, ak2b

*I have a feeling, now that I think about it, that the TX voltage problem might have come from poor grounding on the Linear Amplifier and moving the board around may have temporarily solved the issue.
*11/20/08 Actually, the voltage comes from Q1 through R2.

Last edited by ak2b (2008-11-11 08:36:17)

Hi Gary,

Glad to see you are getting started. Maybe now I won't be so lonely here
I bought my double sided circuit board material about 4 years ago on e-Bay but I can’t remember where. A quick search shows there are still a lot of suppliers though the price looks a little higher than I remember.
Originally, I recorded with Sound Recorder supplied with Windows XP but found it a little limiting. I ended up buying Total Recorder for $18 which was a lot more versatile. http://www.highcriteria.com/ There are probably other programs out there that do an equal or better job and might even be free – I didn’t research it that much.
Have fun and I look forward to hearing/seeing your results.

Tom, ak2b

Gary:
Have you seen my videos page for the Kits and Parts boards? It's at http://golddredgervideo.com/kitsandparts/index.htm and if you haven't seen the mixer one, be sure and take a look.

I haven't had any time to expand it for a while.
Leonard

Hi Leonard
   Yes, I am aware of your videos but need to see them again, later maybe, as I use a wireless connection for internet and my current location is very slow, I'm in southern Washington hauling WindMill blades and expect to be here through the winter, so no prime and fast connection for awhile, unless they upgrade the towers while I'm here ;-)  I'm trying to download the mixer video now, but it does not look good, my connection is really shakey here, If I were back out east 180megs would only be a few short minutes
   And so noted on new topics Tom
  Thanks guys

PS Leonard  , I do have my copy of EMRFD and the 2007 ARRL Handbook with me, so all is not lost  ;-)

kc0wox wrote:

Gary:
Have you seen my videos page for the Kits and Parts boards? It's at http://golddredgervideo.com/kitsandparts/index.htm and if you haven't seen the mixer one, be sure and take a look.

I haven't had any time to expand it for a while.
Leonard

Last edited by W4GNS (2008-11-16 19:51:03)

Take a look at the specs for these relays. http://pdf1.alldatasheet.com/datasheet- … -B301.html If you are interested, I will send you what you need. I have about 100 of them I purchased for another project. I think I paid about 15 cents apiece. I have the dpdt non-latching with a 12 volt coil circuit board mount. V23079-A1011-B301 is the part number of what I have. I can probably get a few thousand more if you needed them. It says they will switch 5 amps or 60 watts. They are a little over 1/4" wide and a little over 1/2" long.
Leonard

*http://tomnyc.no-ip.org/cqwwdxSunday.mp3


I changed the mp3 to a recording made on Sunday with a lower bit rate so the file is smaller. The board where the keyer chip was mounted was loose and hanging as I was doing some other work on the radio. I remounted it and it sounds a lot better. I used a 15W outboard RF amplifier while this was recording. My 4 watts or so  wasn't getting any results as I started later in the morning after the band had changed a bit. The QSK is not quite as good but the results were better.
My original message is posted below as quoted by Gary

Tom, ak2b

*this is a 2MB file