Frequency
The default frequency for 4m
built into the
software is no longer correct. Currently the dial frequency
required for the
band is 70.0910mhz. This means the transmit frequency will
actually be around
70.09250mhz.
To change frequency simply type 70.0910mhz into the dial
frequency window of
the program, then click anywhere in the 'waterfall' display area
and accept the
change.
There is an ongoing debate as to whether the frequency
70.0910mhz should be the
dial (i.e. receive) or the transmit frequency. It appears that
there are errors
in the bandplans published by different organisations that deal
with such
things. It is, therefore, likely that this frequency will change
again in the
near future.
As of today 70.0910mhz is the frequency the few stations on 4m
are using. (July
2012)
However a quick check of the 4m map will show whether this is
true in the
future. It is important to check first. On the other bands
we just take the
software settings for granted. As with many things on 4m Wspr,
frequency cannot
be taken for granted.
Radio Off
Frequency?
Many mutlimode multiband
radios obtain
frequency settings from a central oscillator (simplified
explanation but
useful) which is then multiplied up for different bands.
Any error in this
oscillator will become more apparent with each multiplication.
This is
especially critical at 50mhz and more so at 70mhz. Anyone who
has watched the
50mhz Wspr window for any length of time during an opening will
notice 'worms'
right outside the window. This may indicate that operators are
unaware their
radios are not actually on the correct frequency, even though
the dial is set
correctly.
A few hours observing and it is possible to deduce the
inaccuracy of your radio
(if any). The best way to correct is to adjust the receive dial
a few hz at a
time until your spots agree with the spots of others. GM4FVM
also pointed out
that there is an average frequency for each station in the
'Activity' window of
the Wspr website. This can help if you adjust your radio dial
for a best
fit.
Once you have an idea of the error you have various choices:
1) Leave your radio dial there. Easy and it works. I ran my
FT847 for many
months with the dial set 100hz low, this put it more or less in
the centre of
the window. However it does prevent frequency hopping.
2) Recalibrate your oscillator. Having access to a Flex 1500
with PowerSDR
panadapter screen, and a good signal from GB3BUX, I finally
managed to
recalibrate the oscillator in my FT847. It was simple, but
an accurate source
is required. Details of this adjustment can be found online here
under
'Tweaking The Reference Oscillator'
for the
FT847.
3) Other correction method of your
devising...
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