Experimenter hf net organizing

Frank Gentges fgentges at mindspring.com
Thu Aug 24 22:18:35 CDT 2006


You pose some interesting questions.

David A Aitcheson - KB3EFS wrote:
> Frank,
> Has any consideration been given to doing a kit for this antenna
> project?
AMRAD has not wanted to get into the kit business like some other groups 
have done.  Historically, kits get clubs into trouble where members 
don't want to spend time putting together kits, builders that have 
unrealistic expectations, checks bounce etc.  As time progresses, I may 
choose to do some kits at my own company.  Putting these up on eBay with 
a "Buy it Now" using PayPal could streamline the process.
> On first glance this antenna would be the "ideal standard" for a station
> that is going to be set up as a lurker.  Say a _RX only_ 10m or 20m
> station that is being run my a SWL or a Technician licensed ham; or for
> that matter a school that does not have a licensed ham on staff but the
> teacher wants to promote ham radio.
A good learning experience for students.
> My thinking is... a standard antenna, and a standard receiver (RX-320)
> should equal a standard system that would yield repeatable and results
> from any one signal source.  Thus given: station A received at 1, 2, 3,
> 4, etc. would only vary due to propagation differences caused by
> ionospheric changes. The same should be measurable in cases of B, C, D,
> etc. transmitting to 1, 2, 3, 4, etc.
Yes.  A lot of receiving variables can be eliminated.
> If the transmitters are all of the same make/model and set to the same
> power levels and feeding as nearly identical antennas as possible with
> the controlling being done by (maybe networked) PIC controllers; then
> true scientific studies can really begin I think.
You have good thoughts.  I like the idea of teaching students to collect 
data and then to try and make sense out of it.  Maybe we can make some 
of them into hams with interest in HF radio.
> Have I interpreted correctly your plans. Thoughts?
You are adding to my thinking here.  We may end up an aggregate of fine 
work here.  If we can break the project into small pieces then each 
person can add their part and nobody has to do a big effort for the 

I would like to piggyback short text messages onto the probe signals.  
Essentially a 24/7 data link on HF.

I think I could make the active antenna better with just a bit of effort 
and time. I have had past suggestions for kits and for assembled 
antennas.  Maybe I need to rethink how I could do this.

Frank K0BRA
> 73
> Dave - KB3EFS(/2) Tech. [FN24bi]
> Web Master http://www.propnet.org
> Frank Gentges wrote:
>> Terry and all,
>> Terry Fox wrote:
>>> For a first step for receive-only stations, I could probably get an 
>>> RX-320 or PCR-1000 receiver running with an active antenna (Frank's 
>>> e-field probe) fairly quickly.  I could use that for both our work 
>>> here, plus the propnet - timehare the radio via the computer.
>>> Frank, maybe we should look at standardizing a receive package with an
>>> RX-320, active antenna (antenna tuning driven via computer and cheap 
>>> A/D
>>> converter), plus some sort of cheap computer as we have been talking 
>>> about.
>>> Would the LF active antenna up to 10 meters?  I don't remember the 
>>> specs,
>>> and a lot of books, magazines, etc are still packed up somewhere 
>>> (garage).
>> First, the RX-320 should do well at HF without the AMRAD LF 
>> modification.  Thus, use it right out of the box.
>> Second, the AMRAD Active antenna can be built with the J310 JFET 
>> instead of the high performance CP-666 JFET.  For most users that 
>> should do the job.  You can use the PC board kit and a J310 without 
>> the complexity of the heat sink.  For the HF use. a whip longer than 
>> the one meter would be a real help.  We would keep the PVC pipe 
>> fittings and use 12 volts DC for power.  The transformer could be the 
>> same or a substitute.  We were fighting interwinding capacitance to 
>> keep power line noise coupling down for LF use.  It is not so much a 
>> problem at HF and everything gets simpler.
>> Once I get some time (September perhaps?) I can build up a "standard 
>> package" for our HF work and write it up in the newsletter so 
>> everyone can duplicate it easily.  This is not that hard or time 
>> consuming.
>> Then everyone else can concentrate on the other parts of the problem 
>> and propnet.
>> Perhaps a SoftRock receiver variant can be worked in here someplace 
>> down the line.
>> For a refresher on the antenna go to the AMRAD web page on it at
>> http://www.amrad.org/projects/lf/actant/index.htm
>> A link to the original article is provided along with many later 
>> notes on the construction.
>> Frank
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