Sorry Tom this time you may be wrong.
I use this IC 751A switcher OUTSIDE the transceiver all the time in my
portable station with very little problems - I hear only some tiny carriers
wandering around on 80. I use a windom wire antenna and had some problems
before, before they rebuild the open air power lines that earlier were
closer the antenna. These power lines are open air lines and extend up to 2
kilometers from the summerhouse and are nowadays below earth close to the
antenna. When I had noise problems the power lines were pretty close to the
antenna, say 60 meters.
Even with very much filtering on the switcher mains side there are always
something left way down and with the long power line acting as a huge long
wire antenna coupling to another wire antenna, eg my windom, there should
acually be more QRM than I have right now.
But, I had a problem on two meters with an IC 706 that had some garbage
outside the SSB channel. I assume it was the switcher residual ripple, noise
and spikes modulating the rig. Me and my buddy used some ten element
antennas and the two mweter noise level is very low in our QTH:s. Also, the
706 synthesizer is not very good of course adding to the problem.
Yes? de Hans
----------
>Från: "Tom Rauch" <w8ji@contesting.com>
>Till: amps@contesting.com, Radio WC6W <wc6w@juno.com>
>Ämne: Re: [AMPS] Portable linear using a DAF?
>Datum: tis 31 okt 2000 03.55
>
>
>I've designed switchers and cleaned up switchers for amateur and
>commercial use at HF stations.
>
>> If you can keep the 2nd & 3rd harmonics of your KW amp from futzing up
>> the neighbors (or your own TV's!), then you can certainly deal with the
>> 20th - 300th harmonics of the switcher.
>
>No sale.
>
>1.) The switcher is a square wave, or at least it should be close to
>one. The PA is a half-sinewave or better, and is already 20 dB
>down on low order harmonics without any filtering.
>
>2.) The TV set is likely on an antenna a long distance away from
>the transmitter, and hopefully not wired into the same outlet and
>sharing the same feedline that connects directly or indirectly to the
>same chassis.
>
>3.) The HF receiver is more sensitive, partially because it has
>narrower bandwidth and hams regularly depend on hearing signals
>at noise floor or just above.
>
>> You could actually shut down the output (phase controlled converter)
>> section of the power supply in receive -- while leaving the PFC running in
>> a discontinuous mode. The plate supply would come up before the antenna
>> relay can switch, so there would be no noticeable delay.
>
>That might be an acceptable solution.
>
>> >Shielding a high-power high-frequency switcher from a receiver
>> >connected to an antenna that might be fractions of a wavelength
>> >away is a royal pain.
>>
>> It works fine when I build it here.
>
>You should do more of them then, and sell them. Most other
>people aren't as successful as you are.
>
>> I have two "factory made" switchers in my 4CX1500B amp (one encased, the
>> other open frame). They were both noisy as hell in the open monitoring
>> with a receive antenna a couple feet away -- you could hear them all the
>> way up to 30 MHz! In the cabinet, and properly line filtered, you can't
>> hear a squeak out of them.
>
>You win. These endless arguments are too time consuming.
>
>I do suggest you go into business selling them, because every last
>one of the switchers in the amateur market can be heard on
>receivers when the antenna is close by. The switcher that came
>inside my IC751A is laying in the scrap pile, waiting for a magic
>touch.
>73, Tom W8JI
>w8ji@contesting.com
>
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>
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