"tom" wrote in message
. ..

snip

One thing to remember is you generally do not want elements that are
electrically connected to the boom. The connection is usually not very
good and eventually corrodes. This makes the antenna detune in an
unpredictable manner.

That said, you can weld elements to the boom, which works.

You are better off using insulated elements with inserts in the boom holes
such as Delrin.

This will change the correction factor, but that is a known.

tom
K0TAR


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're still up
there.

If I were to continue in that vein, I could weld (torch solder, really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)

On 2/23/2013 11:41 PM, Sal wrote:


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're still up
there.

If I were to continue in that vein, I could weld (torch solder, really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)



A good source is VE7BQH, Lionel. He has a lot of info related to EME
antennas that are as well engineered as possible for obvious reasons.

I've never looked at his correction factors as I have ones for through
the boom insulated that I know work for my build type. My corrections
are from WB0TEM.

What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR

On 2/24/2013 8:43 PM, tom wrote:
On 2/23/2013 11:41 PM, Sal wrote:


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're
still up
there.

If I were to continue in that vein, I could weld (torch solder,
really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)



A good source is VE7BQH, Lionel. He has a lot of info related to EME
antennas that are as well engineered as possible for obvious reasons.

I've never looked at his correction factors as I have ones for through
the boom insulated that I know work for my build type. My corrections
are from WB0TEM.

What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR


I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea.
And it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR

On 2/24/2013 9:13 PM, tom wrote:
I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea. And
it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR


Here's a reference that mentions reasons for not using uninsulated
through the boom connectio9ns. And has some nice graphs on insulated
through the boom.

http://g7rau.demon.co.uk/sm5bsz/antennas/sa/others.htm

tom
K0TAR

"tom" wrote in message
. ..
On 2/24/2013 9:13 PM, tom wrote:
I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea. And
it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR


Here's a reference that mentions reasons for not using uninsulated through
the boom connectio9ns. And has some nice graphs on insulated through the
boom.

http://g7rau.demon.co.uk/sm5bsz/antennas/sa/others.htm

tom
K0TAR



OK, I'm convinced. What I need is some lightweight non-metallic material
for the
boom and I can build with the numbers I have for element lengths. I'll hit
the stores
in the morning.

I'll try a T-match, too.

"Sal"

"tom" wrote in message
. ..
On 2/23/2013 11:41 PM, Sal wrote:

snip


What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR


BANDS: This is a 220 beam intended for roof mount on my
daughter/son-in-law's house in Livermore CA to see if we can hit the Condor
Connection, which is all on 220. I'm in San Diego, with a nearby Condor
machine. My newly-licensed son-in-law thinks it would be a hoot if we could
talk directly, home-to-home. (I don't want to encourage him to buy an HF
rig for possible use on 10m, since fickle propagation has the potential to
be a buzz kill for a new ham. Upgrade to General is an unknown. He's not
ready for IRLP.)

Condor has two possible repeaters, one on Mount Hamilton (24 mi, by San
Jose) and one on Mount Vaca (50 mi.). Neither is a slam dunk from Livermore
because of terrain blockage. I'm hoping 50W & 10 dB gain will work. I did
some Longley Rice modeling here

http://lrcov.crc.ca/main/ and I'm hopeful.

I have alternate possibilities. The WIN System has 440-band repeaters on Mt
Oso (25 mi.) and on Loma Prieta (40 mi.) but also with terrain issues. ( I
already have a 26-element 440 beam; it models out to about 14 dBd gain.)

Those distances would be no problem except for the blockage. I can do 80
miles with 5 watts off an omni if my RF's don't bump into nuthin' first.

I expect the finished 220 beam to have about 10dBd gain and I have 50 watts
available.

Thanks for the link to Lionel's info. I'll check itout.

"Sal"
(KD6VKW)

On 2/25/2013 12:38 AM, Sal wrote:

BANDS: This is a 220 beam intended for roof mount on my
daughter/son-in-law's house in Livermore CA to see if we can hit the Condor
Connection, which is all on 220. I'm in San Diego, with a nearby Condor
machine. My newly-licensed son-in-law thinks it would be a hoot if we could
talk directly, home-to-home. (I don't want to encourage him to buy an HF
rig for possible use on 10m, since fickle propagation has the potential to
be a buzz kill for a new ham. Upgrade to General is an unknown. He's not
ready for IRLP.)

Condor has two possible repeaters, one on Mount Hamilton (24 mi, by San
Jose) and one on Mount Vaca (50 mi.). Neither is a slam dunk from Livermore
because of terrain blockage. I'm hoping 50W & 10 dB gain will work. I did
some Longley Rice modeling here

http://lrcov.crc.ca/main/ and I'm hopeful.

I have alternate possibilities. The WIN System has 440-band repeaters on Mt
Oso (25 mi.) and on Loma Prieta (40 mi.) but also with terrain issues. ( I
already have a 26-element 440 beam; it models out to about 14 dBd gain.)

Those distances would be no problem except for the blockage. I can do 80
miles with 5 watts off an omni if my RF's don't bump into nuthin' first.

I expect the finished 220 beam to have about 10dBd gain and I have 50 watts
available.

Thanks for the link to Lionel's info. I'll check itout.

"Sal"
(KD6VKW)



Sounds like a plan. Good luck.

If there are any 6m machines around the terrain becomes a lot less of a
problem. If, of course, you have a 6m FM rig. Around here, Minneapolis
metro, we have a few machines that have multiple inputs and outputs.
(Not really, they are individual cross-linked rptrs, but that's just
details). Maybe your area has some.

tom
K0TAR

Sounds like a plan. Good luck.

If there are any 6m machines around the terrain becomes a lot less of a
problem. If, of course, you have a 6m FM rig. Around here, Minneapolis
metro, we have a few machines that have multiple inputs and outputs. (Not
really, they are individual cross-linked rptrs, but that's just details).
Maybe your area has some.

tom
K0TAR

Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

On 2/25/2013 9:50 PM, Sal wrote:


Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

So what you need is a design that will fit on an 8 foot boom. About 7
feet 11 and a half inches. I will see what might work well.

How much was the channel?

tom
K0TAR

"tom" wrote in message
...
On 2/25/2013 9:50 PM, Sal wrote:


Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore
to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out
of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

So what you need is a design that will fit on an 8 foot boom. About 7
feet 11 and a half inches. I will see what might work well.

How much was the channel?

tom
K0TAR


"I will see what might work well." So, do you think the design from the
antenna book is less than ideal?

The channel is priced at $15.94. I will put some masking tape on my piece
of channel, mark off element positions from various designs, attach the
elements temporarily (tape) and evaluate the resulting antenna.

I will set up a makeshift antenna range, with (1) my tracking generator
feeding a 220 whip radiating from my lawn while (2) a helper in the driveway
aims the antenna and while (3) it send its receive signal into the shack
where I, aka His Royal Hamminess, notes the received signal at various
azimuths. (We don't need any stinkin' anechoic chambers.)

Professionally, I've made quantitative measurements of field strength ...
Singer NM-25, anyone? ... but I have nothing approaching modern precision
gear as that which rents for hundreds of dollars a week.

RELATED: If you know, why do some yagis designs place the first director
quite a bit closer to the DE than the rest of the directors' spacing? In
other yagi designs, the spacing of the directors is relatively consistent,
where DE-to-first-director is about equal to the spacing of the remaining
directors. I haven't seen that difference explained ... yet. Thanks.

"Sal"