Hi Stefan, Clemens
When I said <<Most of the time only to discover that their pricy Icom is almost
deaf>>
I mean that the average ham with an average Icom, or any other Japanese off the
shelf rig
is normally unable to detect signals on MF. So, this bands simple DO NOT EXIST
as ham bands
for most of the ham community
Not being my intention to start into a "Deep Search" discussion about Icom
performances, the key
factor is not probably the rig but as has been pointed by Stefan: Local QRM and
wrong antenna match for MF
>Local QRM. But often this is caused by a non-optimal RX-antenna configuration!
>If you put some wire into the RX input and use
>the house-earth as the counterpoise you will likely get that result. But if
>they have a small garden and can run a large earth >rod into the ground,
>resonate and match their dipole for 40m against it, feed the signal
>galvanically decoupled to their RX,
>things may look completely different! Or if they try an active antenna like
>the PA0RDT-antenna from their balcony..
>Worth to create a website or sharing some photos to that forum...
In Spain people live in flats. Having a backyard garden is not usual. That's
why we have a law which permits
to install the antenna in the building WITHOUT asking for permission to the
rest of the community owners. We
just need to get a project aproved by the PTT and executed by an authorized
company to check that all matches
And an insurance covering it all. But having real ground rods is not usual.
Just house-earth wiring :-(
Actually Ramiro, EA4NZ has made a great improvement in his urban Rx dealing
with lot of QRM. Will be very helpful
to publish his work. So others can benefit from his experience
>This is exactly why i say that there must be QRO stations on the band!!!!!!!!!
>...to generate a first detectable signal for a >(still) sub-optimal
>RX-system!! :-)
Absolutely !
People first try to Rx something. If there is nothing heard they automatically
hang the "Out of order Band"
and QSY to 80,40m, etc. I bet this happens to 160m too. But the most amazing is
that this concept is also
applied to VHF and microwaves. "Didn't heard anything"."There is nobody there"
.... %-)
>It is a nice construction but class-E PAs need an exact tuning, i.e. a very
>good SWR. 1:1.5 can destroy the PA! A high-Q
>antenna can quickly destroy the PA.
Indeed ! Even with a dummy load, first test was using a signal generator and I
wrongly changed the QRG to 430KHz
That was my first mosfet burned out :-O
>Nice construction.
>First i would recommend to replace the IRF510 by a IRF540, IRF540N, IRFZ48N or
>so. These are better for 14V and will give you
>more power.
Thank you for the info. They are now on the order list :-)
>The 7667 can handle them, i.e. their input C is still low enough. But, a
>class-E has a defined output power at a certain
>voltage. Tuning is critical. If your antenna is slightly detuned, or a C
>becomes warm, the working point can quickly drift
> away. So you cannot really squeeze out the maximum theoretical power unless
> you optimise things endlessly.
>I would recommend a class-D PA running at 14V, using the 7667 as a driver....
>I have a running design, easily generating 100W
> at 12V. But you need an opposite phase signal on the input and i don't know
> what the output of the U3 is like. Is it a sine
>wave at 50 Ohm output impdance or is it a rectangular high-Z output like the
>Raspberry provides? A small ferrite transformer
> with a trifilar winding can provide that opposite phase signal. It's all no
> miracle and sounds more complex than it is :-)
U3 outputs the signal from a DDS or actually in the new version using a SiLabs
PLL. There is sine and square output
Bet you are describing the same system used in a softrock to get a bi-fase
signal from the antenna. See T1
http://fivedash.com/resource/LiteIISchematic.pdf
This can be included at the input of the PA, so it can be feed from shack with
a coax line
>> Yesterday I tried it at 24V. Little difference. Got 8 times antenna current.
>Antenna current or PA DC input current? I assume the PA-efficiency
>dramatically decreased in that test :-)
I mean RF antenna current. As my measure is not calibrated I just tell you in
therms of gain (8 times)
Yes, really no worth to run it at 24V and very risky for the mosfet
Are you planning to produce a PCB for your 100w PA ?? May be there are more
people interested
Have seen DJ0ABR 500w project but not sure if he is selling the boards or have
interest in building more PA
http://www.dj0abr.de/index_english.html
Last IRF510 of the batch running tonight. Lets see if all goes Ok at 14V
73 de Luis
EA5DOM
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