2m/70cm SWR Meter?

[BB]

Hi all,

I was just wondering if I could ask a question about SWR meters for
2m/70cm...

I am building some antennas and am going to need to purchase a meter, and
was wondering if this was a case where you "get what you pay for"... I
checked on ebay, and there were some meters starting at the $30 price
range.... the next step were some OPEK meters for around $60... would I
be okay going with one of these or another used or no-name machine, or
should I look to an established dealer for a potentially better quality
product?

Thanks for the input and suggestions... I have been almost an exclusively
HT guy up to now, and am looking to expand my horizons a bit...

:-)

73,

Bill Berris, KF6CNP
Salida, CA

[Bob Bob]

Hi Bill

Generally speaking inline SWR and power measuring devices have a
operating frequency "rating". My Diammond box for example has two
sensors that allow 1.8-160MHz and 140-525MHz depending which holes you
plug it into in the back. There are two main problems in getting wide
freq coverage, one is to preserve the through impedence and the other is
to make the power sensing element work over the wide frequency range.

Most of the cheapies will be no doubt made for the CB market and for
that of course calibration will be an issue. You'll also find they may
not work on lower freqs as the sensing elements arent a large enough
part of a 1/4 wavelength to get enough volts to the meter. They also
present a significant impedance bump to RF at higher freqs that if
nothing else would invalidate your tuning efforts.

So in short have a look mainly at the specs re frequency. Oh and dont
forget the connector interface as well.

What would I buy if money was no object? Probably a Bird or make
something from a couple of directional couplers and the PC/laptop. My
Diammond came from RF Parts in CA for I think around USD150, but I cant
say I have bought/know enough to say they are the best value etc...

Cheers Bob W5/VK2YQA East Texas,

Post by BB
Hi all,
I was just wondering if I could ask a question about SWR meters for
2m/70cm...

[Big Al]

Best value for your money, I would buy a Bird or an MFJ antenna anylizer.
The anylizer would likely do a better job of figuring out the optimum
frequency for any antenna and you could plot an swr curve verses frequency.

73...de ve7agw

Post by Bob Bob
Hi Bill
Generally speaking inline SWR and power measuring devices have a operating
frequency "rating". My Diammond box for example has two sensors that allow
1.8-160MHz and 140-525MHz depending which holes you plug it into in the
back. There are two main problems in getting wide freq coverage, one is to
preserve the through impedence and the other is to make the power sensing
element work over the wide frequency range.
Most of the cheapies will be no doubt made for the CB market and for that
of course calibration will be an issue. You'll also find they may not work
on lower freqs as the sensing elements arent a large enough part of a 1/4
wavelength to get enough volts to the meter. They also present a
significant impedance bump to RF at higher freqs that if nothing else
would invalidate your tuning efforts.
So in short have a look mainly at the specs re frequency. Oh and dont
forget the connector interface as well.
What would I buy if money was no object? Probably a Bird or make something
from a couple of directional couplers and the PC/laptop. My Diammond came
from RF Parts in CA for I think around USD150, but I cant say I have
bought/know enough to say they are the best value etc...
Cheers Bob W5/VK2YQA East Texas,

Post by BB
Hi all,
I was just wondering if I could ask a question about SWR meters for
2m/70cm...

[werty]

All Radios have power output protection circuits .
Hook into these with a cheap DMM to see what is being reflected .


Now use the Freq dial to chart and plot the antennas 50 ohm points .
Or see if MightyFineJunk MFJ has a UHF box ( I have the 209 ) .
I prefer opening the radio and using schematic to find a LOW freq
method of sampling cause they must sample to protect . Why not
use their sampler .


The ARRL HB has a Digital SWR project , but it still requires
uncommon
tech ability to create the UHF coupler ! It is easy at VHF , hard at
UHF .
This Meter uses the math function (divide ) of the ICL7106 to
ratio the
FWD/REFTD waves . But the big problem is still the coupler !

My Icom 746pro ( H.F. > VHF ) has SWR built in , so i just lower
power
and chart the antenna . But no help on UHF .

I hate using the old Diode and terminating R in a coupler above 400
MHZ .
But an article in HamRadio showed a cleaned up cheapo worked well at
450 ! Ham Radio was the greatest mag ever for techies ! The
microfische
is worth thousands !


KC7CC