Tuning a Discone and SWR's
 

My SWR's are basically flat on the lower end of the 2m scale, but there is a
significant jump starting at 146.000 thru 147.999. Starting at 147.000,
it's pushing the 3:1 threshold and going over the 3:1 threshold the higher
in the freq band I go.

I have a discone antenna and would like some suggestions as to tuning
methods. From what I know, if the SWR's are high on the 'top' end of the
range, the main vertical whip needs to be trimmed.

Does that sound right or is there something else I need to check on first?

Thanks.

Macman wrote:

My SWR's are basically flat on the lower end of the 2m scale, but there is a
significant jump starting at 146.000 thru 147.999. Starting at 147.000,
it's pushing the 3:1 threshold and going over the 3:1 threshold the higher
in the freq band I go.

I have a discone antenna and would like some suggestions as to tuning
methods. From what I know, if the SWR's are high on the 'top' end of the
range, the main vertical whip needs to be trimmed.

Does that sound right or is there something else I need to check on first?

Thanks.

Makes sense to me.

Thanks for input, as always, it has proven very helpful.
Now, time to make a trip up the tower!

Macman wrote:

Thanks for input, as always, it has proven very helpful.
Now, time to make a trip up the tower!

Trim slowly!

Yeah, about 1/8 inch at a time. At least, that's what I've read.


"N8KDV" wrote in message
...


Macman wrote:

Thanks for input, as always, it has proven very helpful.
Now, time to make a trip up the tower!

Trim slowly!

Measure TWICE and cut ONCE my uncle always used to tell me G. He used to
make boats, and I used to help him soap the scews so they could be driven in
easier. Be careful up there, and I wish you success. Let us know how you
come out.



"Macman" wrote in message
...
Yeah, about 1/8 inch at a time. At least, that's what I've read.


"N8KDV" wrote in message
...


Macman wrote:

Thanks for input, as always, it has proven very helpful.
Now, time to make a trip up the tower!

Trim slowly!

Macman wrote:

My SWR's are basically flat on the lower end of the 2m scale, but there is a
significant jump starting at 146.000 thru 147.999. Starting at 147.000,
it's pushing the 3:1 threshold and going over the 3:1 threshold the higher
in the freq band I go.

I have a discone antenna and would like some suggestions as to tuning
methods. From what I know, if the SWR's are high on the 'top' end of the
range, the main vertical whip needs to be trimmed.

Does that sound right or is there something else I need to check on first?

Thanks.


If by main vertical whip you mean a whip (possibly with a loading coil
in the bottom) extending up from the top of the disc; that would be for
the bottom end of the frequency range - i.e. probably around 30 - 50MHz.

At 2 Meters it is more likely that the disc and cone dimensions are
involved.

I'm basing this on my ICOM discone which works fine from 144MHz up even
if the vertical whip is completely removed. The whip only seems to have
any effect on 6 Meters.

Dave

Thank you Dave. The elements radiating down and out (the cone area) has two
elements that telescope out. I think some fine adjustments in or out, at
that point may help.

And by the way, thanks for the info regarding the vertical whip section and
has it is centered load on it. This is my first discone and wasn't too sure
exactly how to go about tuning.


"Dave Holford" wrote in message
...


Macman wrote:

My SWR's are basically flat on the lower end of the 2m scale, but there
is a
significant jump starting at 146.000 thru 147.999. Starting at 147.000,
it's pushing the 3:1 threshold and going over the 3:1 threshold the
higher
in the freq band I go.

I have a discone antenna and would like some suggestions as to tuning
methods. From what I know, if the SWR's are high on the 'top' end of
the
range, the main vertical whip needs to be trimmed.

Does that sound right or is there something else I need to check on
first?

Thanks.


If by main vertical whip you mean a whip (possibly with a loading coil
in the bottom) extending up from the top of the disc; that would be for
the bottom end of the frequency range - i.e. probably around 30 - 50MHz.

At 2 Meters it is more likely that the disc and cone dimensions are
involved.

I'm basing this on my ICOM discone which works fine from 144MHz up even
if the vertical whip is completely removed. The whip only seems to have
any effect on 6 Meters.

Dave

On Thu, 01 Apr 2004 18:17:28 GMT, "Maximus" wrote:

Measure TWICE and cut ONCE my uncle always used to tell me G. He used to
make boats, and I used to help him soap the scews so they could be driven in
easier. Be careful up there, and I wish you success. Let us know how you
come out.



I thought the phrase (adjusted for big corporations) was "Measure
once, cut twice then give the tape measure a poor performance
evaluation."

Macman wrote:

My SWR's are basically flat on the lower end of the 2m scale, but there is a
significant jump starting at 146.000 thru 147.999. Starting at 147.000,
it's pushing the 3:1 threshold and going over the 3:1 threshold the higher
in the freq band I go.

I have a discone antenna and would like some suggestions as to tuning
methods. From what I know, if the SWR's are high on the 'top' end of the
range, the main vertical whip needs to be trimmed.

Does that sound right or is there something else I need to check on first?

Thanks.


You are talking like a cber, SWR is singular not SWR's(plural)