I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. Due to a short mast, the Diamond is virtually sitting on top
of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of the
coax. The MFJ 259B reads 1.9:1 at 144 mHz. Presumably the SWR is a bit
higher at the antenna connector.

If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR at
144 to go down? How much separation is needed?

Chuck Forsberg WA7KGX N2469R wrote in
:

I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. Due to a short mast, the Diamond is virtually sitting on
top of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

Ok, from TLLC (http://www.vk1od.net/calc/tl/tllc.php) you have about
1.1dB of line loss if everything is in good condition.


The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of
the coax. The MFJ 259B reads 1.9:1 at 144 mHz. Presumably the SWR is
a bit higher at the antenna connector.

I assume all readings were made with the same instrument.

Your load end VSWR at minimum is close to 1.3, which is typical of those
type of things. The frequency of the minimum does seem a bit high.


If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR
at 144 to go down? How much separation is needed?

I am a bit surprised that it is that far off, and wouldn't expect a lot
of change in raising it... but you only know if you try it.

Have you used / measured it in other scenarios?

Have you measured the VSWR characteristic using a conventional
reflectometer style instrument at modest power? Does it agree with the
'259B?

Owen

On Apr 25, 3:16*pm, Chuck Forsberg WA7KGX N2469R
wrote:
I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. *Due to a short mast, the Diamond is virtually sitting on top
of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of the
coax. *The MFJ 259B reads 1.9:1 at 144 mHz. *Presumably the SWR is a bit
higher at the antenna connector.

If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR at
144 to go down? *How much separation is needed?

The 9913 is infamous for getting water inside of it. This is usally
indicated bu an unusually low and broad banded VSWR reading. There
should be some good info on the internet about "stacking antennas" I
think some of those who loiter on this NG have written some papers on
it, I seem to remember Owen but I may be wrong.

Jimmie

On Apr 25, 4:22*pm, Owen Duffy wrote:
Chuck Forsberg WA7KGX N2469R wrote :

I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. *Due to a short mast, the Diamond is virtually sitting on
top of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

Ok, from TLLC (http://www.vk1od.net/calc/tl/tllc.php) you have about
1.1dB of line loss if everything is in good condition.



The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of
the coax. *The MFJ 259B reads 1.9:1 at 144 mHz. *Presumably the SWR is
a bit higher at the antenna connector.

I assume all readings were made with the same instrument.

Your load end VSWR at minimum is close to 1.3, which is typical of those
type of things. The frequency of the minimum does seem a bit high.



If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR
at 144 to go down? *How much separation is needed?

I am a bit surprised that it is that far off, and wouldn't expect a lot
of change in raising it... but you only know if you try it.

Have you used / measured it in other scenarios?

Have you measured the VSWR characteristic using a conventional
reflectometer style instrument at modest power? Does it agree with the
'259B?

Owen

Owen, didn't you write a paper on stacking antennas.

Jimmie

On Apr 25, 6:30*pm, JIMMIE wrote:
On Apr 25, 4:22*pm, Owen Duffy wrote:



Chuck Forsberg WA7KGX N2469R wrote :

I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. *Due to a short mast, the Diamond is virtually sitting on
top of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

Ok, from TLLC (http://www.vk1od.net/calc/tl/tllc.php) you have about
1.1dB of line loss if everything is in good condition.

The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of
the coax. *The MFJ 259B reads 1.9:1 at 144 mHz. *Presumably the SWR is
a bit higher at the antenna connector.

I assume all readings were made with the same instrument.

Your load end VSWR at minimum is close to 1.3, which is typical of those
type of things. The frequency of the minimum does seem a bit high.

If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR
at 144 to go down? *How much separation is needed?

I am a bit surprised that it is that far off, and wouldn't expect a lot
of change in raising it... but you only know if you try it.

Have you used / measured it in other scenarios?

Have you measured the VSWR characteristic using a conventional
reflectometer style instrument at modest power? Does it agree with the
'259B?

Owen

Owen, didn't you write a paper on stacking antennas.

Jimmie

Perhaps I was thinking about Ian White.

Jimmie

JIMMIE wrote in
:

....

Owen, didn't you write a paper on stacking antennas.

Jimmie

Jimmie, I did write a paper on optimum stacking distance for DL6WU long
Yagis, but that is quite a different situation to that in which Chuck finds
himself.

Your comment about the coax is valid, and all elements should be checked.

I might also add Chuck, that some folk have described minimum VSWR being
shifted, and attributed it to faulty ceramic caps in the network at the
base of the antenna.

But first, does it behave properly when mounted in the clear. If so, it
probably isn't faulty, but its environment the likely cause.

Owen

On Sun, 25 Apr 2010 15:29:20 -0700, JIMMIE wrote:

On Apr 25, 3:16Â*pm, Chuck Forsberg WA7KGX N2469R wrote:
I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. Â*Due to a short mast, the Diamond is virtually sitting on
top of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of
the coax. Â*The MFJ 259B reads 1.9:1 at 144 mHz. Â*Presumably the SWR is
a bit higher at the antenna connector.

If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR
at 144 to go down? Â*How much separation is needed?

The 9913 is infamous for getting water inside of it. This is usally
indicated bu an unusually low and broad banded VSWR reading. There
should be some good info on the internet about "stacking antennas" I
think some of those who loiter on this NG have written some papers on
it, I seem to remember Owen but I may be wrong.

Jimmie

I checked the 9913 and discarded some of it where there had been a hint
of water ingress. In this instance, the SWR is a bit higher than Diamond
shows in its chart. The SWR minimum at first glance is no broader than
spec - it's just at the high end of the band instead of the middle.

Later this week I should know if separating it further from the Thunderbird
will change things.