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Re: First HF Radio?


 

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Hi, Dave, I would be the first to admit that the 7300 does not have a bulletproof receiver.

However, the Alachua County team set up five HF antennas, four of which were in some proximity at the freedom center at our park, based on a 50 foot tower provided for by the county, and one of which was an off-center Fed sloping vertical maybe 100 150 yards south. ? ? It was a ?4F operation with a 6 m station at the alternate site for our EOC?

We did manage to operate with only ICOM 7300s, for 22 hours, on eight hours of which we were having two stations on the same band. ? Sometimes as close as CW and FT 8/FT4. ?

We did have some difficulties. People had to learn how to turn on the ICOM attenuator, and they also had to learn not to use preamplifiers!!! ?At one point the 40 m CW station was coming in on three receivers, due to less than wonderful choices.

After people learned about these tricks and connected up all of the bandpass filters we had built, we proceeded the entire rest of the contest with minimal difficulty. ? Over 1200 contacts, which for our group was phenomenal, because we are still relatively new at this!!!?

We did organize our antennas as much as possible to separate them. ?Generally by offsetting them from the tower. See the photograph on page one. ?

We just don¡¯t have fantastic equipment, and we decided to go with what we had. ?

Preliminary measurements done at our dress rehearsal with a similar antenna set up suggested we had separations between 30 and 60 DB on various bands between various antennas. ?We were not always able to use the optimal separated antennas. ? Our calculation suggested we needed 50 DB or more isolation, and our band pass filters and receiver attenuators helped out a lot

I operated several hours at the GOTA ?station, without any bandpass filters, often on the same band as a digital station A few tens of kHz away while I operated CW. By using the attenuator I got away with it.

Most of us just don¡¯t have the money for much better than a 7300, and that has been a step up for most of us! ? More power to your group for having better equipment!

73,
Gordon Kx4z



On Jul 1, 2023, at 15:29, ajparent1/kb1gmx <kb1gmx@...> wrote:

?We ahve run 4A for decades using many radios.? While the K3/K3S are great?
we have had a mix of IC7300 and IC7610s? without resorting to band pass fitlers.

(3 of the 4 are CW, phone, data,) we also run a GOTA usually with IC7610.

IT works and no issues IF: No one over drives the radios (all!) and we spread
the antennas over a 600Ft area.? When we did have two stations withing one
antenna length the usual problem was gross RX overload.? ?The other is
many radios at less than 12.6V at the rear of the radio will start to get dirty
and at 11.7V will be dirty on TX.? Every one at our site went to LiFePo4
to avoid that as lead voltage sags greatly by time you pulled 40% of the
Ah capacity.? ?Or they use charger+genset to keep the battery up.

Another way is one genset, two power supplies, two radios as that
sets up common mode RF path. Ferrite (lots of it) is your friend.

I've seen pictures (even this year) of two people on the same band at the same
table at 100W (less an issue with QRP) wondering why they were beating
each other up.

In the end there are many radios we literally banned, TS440, TS570, ts2000,
IC706(all) and a bunch of other oldies.? One answer to anyone that says yabut,
Experience with massive and severe keyed noise on multiple bands and
band filters were not totally effective.

That said why are we even talking about anything outside the bitx group of radios?

The monoband bitx are OK on TX but on rx they are still easily overloaded by even
K3S in the FD circle.? Sbitx is power hungry and I've not even considered it for the
field. However three hams within .6mi easily overload the reciever.

--
Allison
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Please use the forum, offline and private will go to bit bucket.

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