[CQ-Contest] CQ-Contest Digest, Vol 151, Issue 20

[Bob Henderson]

Mike

Bandpass filters are likely needed for the WARC bands whenever you intend
to listen on those bands while transmitting elsewhere.

Considering the value of BPFs in terms of their harmonic attenuation is a
common folly, except if you run barefoot.

While BPFs certainly do attenuate harmonics, this is all to no avail when
the BPF is installed between transceiver and amplifier.

A Class AB stage fed with a pure sine source has a second harmonic
component of anode current only 6dB down from the fundamental. This means
that unless the drive has a second harmonic larger than -16DB down once
amplified by the PA, its effect on total harmonic output will be
negligible.  This applies similarly to other harmonics.

In other words: If your transceiver is FCC compliant adding BPFs between it
and a following amplifier will yield no benefit in harmonic reduction
whatsoever.

BPFs primarily act to protect receiver front ends from exposure to harmful
levels of fundamental energy.  This is as true for a 6m transceiver as it
is for one at HF.  If you have a 6m yagi co located with say, a 10m yagi or
tribander your 6m transceiver will be exposed to dangerous levels of cross
coupled fundamental energy.

73

Bob, 5B4AGN

Date: Mon, 20 Jul 2015 19:53:24 -0300
> From: "Mike Smith VE9AA" <ve9aa at nbnet.nb.ca>
> To: <cq-contest at contesting.com>
> Subject: Re: [CQ-Contest] seeking 9band bandpass filter unit
> Message-ID: <000601d0c33e$f37e3e30$da7aba90$@nbnet.nb.ca>
> Content-Type: text/plain;       charset="us-ascii"
>
> Charly,
>
>
>
> Since bandpass filters are primarily used in SO2R contesting operation (or
> field day ie: M/M, M/2 type of operations), I have to ask..why would you
> need bandpass filters for the WARC bands !? (no contesting on the WARCs)
>
> Also, since nothing is a harmonic of 6m, nor is any HF band close to 6m as
> a
> harmonic,(except far far away) same query goes for SIX.
>
>
>
> I am not trying to be sarcastic...it's a serious question.
>
>
>
> I too would like to dabble my toe in the SO2R waters, but not at $2000+ to
> get it here to Canada.
>
>
>
> Mike VE9AA
>
> Mike, Coreen & Corey
>
> Keswick Ridge, NB
>
>
>
>
>
>