[600MRG] Some experimenting with toroids vs hollow coils on 630m

[John VE7BDQ]

Very interesting and thanks for posting.  Seems a lot of amateurs are
having great success using a 9:1 or 49:1 toroid to feed a random wire on
HF.  Or so they say,  Tempted to give it a try but I don't have suitable
cores in my junk box. Must be a matter of luck to get the length of the
random wire just right.
 73   John / VE7BDQ



On Wed, Feb 15, 2023 at 6:51 PM Neil Klagge <w0yse at msn.com> wrote:

> The following is just my experience, not a scientific thesis  😉
>
> These are the results of an experiment comparing a FT240-52 with a hollow
> cylindrical coil on the ouput of my 630m IRF510 FET power amplifier for
> 630m.
>
> Transmitter output was 4.5w input to the toroid for this test, but there
> was only 2w left on the output of the toroid, going into the coax to the
> antenna. The KA7OEI-1 Northern Utah SDR was used during midday to decode my
> signal with that core. The results were worse by about 10 dB compared to
> when using the hollow PVC coil. The amplifier ran very warm with the toroid
> even though my fans were running full blast and even though the SWR was
> very low.
>
> Using the same output power of the amplifier, the cylindrical coil got a
> 10 dB stronger report from the SDR.  And, there was negligible heating of
> the amplifier.   (I had similar results with an FT240-43 core the previous
> week).
>
> The #52 core is less than 45% efficient whereas the PVC coil is about 83%
> efficient. The PVC coil wins!
>
>
>
> Next, I experimented with the 52 core at the base of the antenna. I was
> able to get the SWR under 2.0 at the base of the antenna by adding or
> subtracting turns on the core. Inside the shack I could adjust the SWR to
> about 1.2 but the amplifier still ran hot when using the toroid and the
> reports back from the N. Utah SDR were weaker by about 7 dB.
>
> My original coil at the base of the antenna works much better than the 52
> core.
>
> Hoping some will find this useful...
>
> 73
>
>
>
> **´¨) ¸.•´¸.•*´¨) ¸.•*¨) (¸.•´ (¸.•`   Neil *, wØyse, DN41ah, North
> Ogden, Utah 84414
>
>
> My ham radio website: http://w0yse.webs.com/
> <http://wg2xsv.webs.com>
> My Faith website: http://neilsfaith.webs.com/
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