I have nothing here to measure the Q of the trap.

Is there another way of working out the correct frequency needed for the
trap?

The traps are made from RG58 C/U. I think these are a low Q but I'm not
sure.

Andy


"Cecil Moore" wrote in message
...
Andy wrote:
I have a question about traps. I read yesterday that traps should not be
tuned to resonance of the wanted frequency. If I constructed a homebrew
trap for say 7.1 MHz. How far away from this frequency should I tune the
trap?

Should it be tuned higher or lower?

Tune it for lower than the operating frequency to
minimize trap losses. The point to shoot for is
the maximum inductive reactance point which is
at a lower frequency than the parallel resonant
resistance point. How much lower depends upon
the Q of the trap.
--
73, Cecil http://www.w5dxp.com

Andy wrote:
I have nothing here to measure the Q of the trap.
Is there another way of working out the correct frequency needed for the
trap?

Sorry, I would just be guessing. I made my 40m traps
resonant on 7.4 MHz and they worked well over the
40m band. But I never made any measurements or A/B
comparisons.

The traps are made from RG58 C/U. I think these are a low Q but I'm not
sure.

The following web page might be of interest:

http://www.seed-solutions.com/gregor...n/CoaxTrap.htm
--
73, Cecil http://www.w5dxp.com

I've given up on this idea for now. I just can't get any ground wires above
or below ground here at present and the couple of earth rods that I have
sunk in just doesn't do the job.

73 Andy


"Cecil Moore" wrote in message
...
Andy wrote:
I have nothing here to measure the Q of the trap.
Is there another way of working out the correct frequency needed for the
trap?

Sorry, I would just be guessing. I made my 40m traps
resonant on 7.4 MHz and they worked well over the
40m band. But I never made any measurements or A/B
comparisons.

The traps are made from RG58 C/U. I think these are a low Q but I'm not
sure.

The following web page might be of interest:

http://www.seed-solutions.com/gregor...n/CoaxTrap.htm
--
73, Cecil http://www.w5dxp.com

Andy,
You have learned something though. Those 'ground/earth' rods
aren't all they are cracked up to be, not exactly the 'best' choice in
every case (especially for lower frequencies). Not much consolation,
huh? Oh well, that's the way it goes...
- 'Doc

Hi Doc,
Yep I guess I've learned that earth rods on there own are a no-go for
end-fed wires at those frequencies. I shell know better next time.

73 Andy


wrote in message
...
Andy,
You have learned something though. Those 'ground/earth' rods
aren't all they are cracked up to be, not exactly the 'best' choice in
every case (especially for lower frequencies). Not much consolation,
huh? Oh well, that's the way it goes...
- 'Doc

In message , Andy
writes
wrote in message
...
Andy,
You have learned something though. Those 'ground/earth' rods
aren't all they are cracked up to be, not exactly the 'best' choice in
every case (especially for lower frequencies). Not much consolation,
huh? Oh well, that's the way it goes...
- 'Doc

Hi Doc,
Yep I guess I've learned that earth rods on there own are a no-go for
end-fed wires at those frequencies. I shell know better next time.

73 Andy

This does sound rather defeatist. While ground rods alone may not be the
'ultimate', surely they are usually be adequate for listening-only
purposes?
--
Ian

Ian,
They probably are adequate for 'just listening'. In a lot of cases,
not using a ground works just fine too. Just depends on the
circumstances. Receivers just don't seem to be very 'picky' like
transmitters are. Since the 'ground' can sort of affect where you
hear things from, that's one of those 'things' to consider too.
There are very few 'perfect' antennas or installations, almost all of
them are a compromise in some way. The idea is to make the best of
what you got (Ooooo, is that a can of worms!). And the mostest
important thingy is to have fun at it.
- 'Doc