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Re: ANTENNA INPUT CHARACTERIZATION

KY1K
 

Thanks Tony,

I'm plugging away at it, making some progress. I'm not sure if I can evaluate the I/Q analog outputs without a sound card that has a stereo input, which is what have at the moment. House under construction, the primary computer and some test equipment not available.

If anything, I should call you I think. I appreciate the offer.

The antenna analyzer is available online, or I can send it to you easily (900 KB). I'm applying the output of the unit in mode 1, which gives swr, Xs and Rs for any frequency that the unit is set for.

Here's what I've done so far.

Characterized the antenna input for Xs, Rs and swr as shown on the MFJ 269 antenna analyzer (at 5, 6, 7, 8 and 9 Mhz). Results given in email message. I compared the one you built (which is now my wifes) to the kit I just got done putting together. Your unit runs good, mine is deaf, but has the same output voltage as mine does with no antenna input. Like i said, they appear identical until one plugs in an antenna.

When the antenna is connected, my unit only shows 4 db more noise on the output, the unit you sent shows 20 db more output.

My unit can hear the MFJ oscillator at 20 db above the noise. The same signal is 50 db above the noise on the prebuilt unit you sent.

I have confirmed that each 7408 gate has 7054 Khz on the outputs and that those outputs are getting to the input pins of the analog switch.

I'm curious whether the electrical differences in the antenna input are typical, or whether they are the likely source of the problem. They seem to be quite a bit different than they should be when the results are compared between the 2 softrocks. But, I don't have enough experience to know if they should vary by as much as they do.

I've attached a PDF which shows the results of the input characterization a little better, the email message came through scrambled, not sure why.

At 04:06 PM 10/8/2005, you wrote:

Hi Art,

Not sure I understand your table of data. However, I would be happy to give
you a telepone call and see if we can track down the problem with your
SoftRock. I have worked with a number of others over the phone and I think
it has helped them a bit. If you would be interested in doing that, send me
an e-mail at raparks@... with your telephone number and what time I
should call.

73,
Tony KB9YIG

----- Original Message -----
From: "KY1K" <ky1k@...>
To: <softrock40@...>
Sent: Saturday, October 08, 2005 2:23 PM
Subject: [softrock40] ANTENNA INPUT CHARACTERIZATION


Greetings all,

As previously reported, my softrock is dead-has to be a bone
crushing+ loud signal to be heard. But, the output level to the sound
card appears identical compared with my borrowed and fully functional
softrock. By this I mean that both units put out the same signal
level to the soundcard with no antenna connected....in fact, it's
impossible to tell them apart until a decent antenna is connected.

So, I figured I had a tuned circuit problem between the antenna and
the transformer...but that the power supply, the switch and the logic
was probably working fine.

I borrowed an MFJ antenna analyzer (MFJ-269) and fed the thing into
the antenna input.

I've checked these figures twice, got the same numbers both times.

These measurements were taken on the bench with power applied from
the computer and with the connection made to the sound
card (without antenna attached). I have a fairly high degree of
confidence that the MFJ is in working order, it's used often and has
recently made stubs for 6 meters and the numbers seem reasonable when
hooked up to my 2 meter yagi.

So, here is are the results.

SWR
Rs Xs

5 Mhz 15(12) 12(15) 102(96)
6 Mhz 1.7(3.2) 77(14) 26(12)
7 Mhz 3.8(2.1) 30(24) 63(12)
8 Mhz 2.7(2.4) 113(21) 56(14)
9 Mhz 1.0(5.3) 49(11) 2(25)


Has anyone else had their softrocks hooked up to an antenna analyzer?
The numbers seem like they should be a little closer to each other,
so I'm not sure whether to look at the tuned circuit or elsewhere.
Any suggestions?

HELP!!!!!!

Art



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