<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head><body bgcolor="#FFFFFF" text="#000000">Hi Guys,<br>
<br>
I've not seen the picture of the prototype show up in my email, so I'm
assuming that it's been chopped out. Here's a link to the file on a very
crude server I put together that has the picture.<br>
<br>
<a class="moz-txt-link-freetext" href="http://bnrstuff.duckdns.org/AntennaAnalyzerPrototype.png">http://bnrstuff.duckdns.org/AntennaAnalyzerPrototype.png</a><br>
<br>
I know there must be cloud stuff out there to share pictures and I've
been using Dropbox for many years. I just haven't figured out how to
send the picture without using everyone's email address (which I don't
have). <br>
<br>
73 Bruce<br>
<br>
<br>
<br>
<span>Bruce Raymond wrote on 3/25/2019 4:20 PM:</span><br>
<blockquote type="cite"
cite="mid:a9d8770d-ca46-32ec-1182-8e86447cf690@raymondtech.net">Hi Guys,
<br>
<br>
I ran into trouble with email size on the last blast-o-gram. I don't
know if the picture came through, so I'll send the email again with a
much lower resolution picture. Please ignore this email if the previous
email made it through.
<br>
<br>
Again, any and all feedback is welcome.
<br>
<br>
73 Bruce/ND8I
<br>
<br>
<br>
<br>
Bruce Raymond wrote on 3/24/2019 9:52 PM:
<br>
<blockquote type="cite">Hi Ed and Ricardo,
<br>
<br>Thanks for the feedback. Much appreciated.
<br>
<br>My concept for the antenna analyzer is to combine an Arduino
(computer), Si5351a board (oscillator, frequency set by the Arduino)
and an LCD diisplay. The oscillator drives a simple resistor bridge
with the antenna as one of the legs of the bridge. I'm using an AD8307
log amp to measure the voltage across the bridge. I've attached a
picture of the prototype analyzer.
<br>
<br>The idea is to sweep a range of frequencies to find the resonant
point
and calculate and display the VSWR at that frequency.
<br>
<br>Initially I thought that I could also measure the bandwidth where
the
VSWR of the antenna is 2:1 or less. I wasn't able to get that to work.
After some reflection I realized that there are reactive components
once you get away from resonance that make measuring VSWR impossible
with a resistive bridge.
<br>
<br>I've tried to keep the operation simple. After turning the power on,
you turn the knob (rotary encoder) to set the center frequency of the
sweep; that's shown as "IN:" in the photo. Each click of the knob
changes the frequency by 1 MHz. Then analyzer sweeps from 0.5 - 1.5
times the center frequency. In the case shown (center frequency = 12
MHz), the analyzer sweeps from 6 MHz - 18 MHz. After you set the
center frequency you push the knob to start the sweep. It's fairly
quick - takes about 2 sec to do a sweep. The analyzer should work over
a frequency range of 1-30 MHz. It's possible that the range can be
expanded.
<br>
<br>My objective was to make something that's portable and relatively
cheap, sorta trading accuracy for money. I think it will be accurate
within 5%-10%. Actually, the frequency measurement seems to be
accurate within 10 KHz and the SWR within ~0.1 at resonance.
<br>
<br>This is an open source project, so I'm planning on releasing the
source code into the wild. I'm planning on shipping an preprogrammed
ProMini with the kit so that you don't have to do any programming or
loading of software.
<br>
<br>I have two AD8307 chips in the design. These are smd chips that I'm
going to have presoldered to the pcb so the builder doesn't have to do
that. Everything else is through hole/parts with leads. There are a
couple of other smd chips shown on the prototype. These were part of
another project (mag loop autotuner) and not part of the antenna
analyzer.
<br>
<br>I'm planning on having the analyzer available to show at
Hamvention/Dayton in May and have kits available through TAPR
hopefully in July - if I can get the documentation ready ;-)
<br>
<br>I'm interested in everybody's thoughts and comments. Any and all
feedback is welcome.
<br>
<br>73 Bruce/ND8I
<br>
<br></blockquote>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
hfsig mailing list
<a class="moz-txt-link-abbreviated" href="mailto:hfsig@lists.tapr.org">hfsig@lists.tapr.org</a>
<a class="moz-txt-link-freetext" href="http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org">http://lists.tapr.org/mailman/listinfo/hfsig_lists.tapr.org</a>
</pre>
</blockquote>
<br>
</body></html>