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 2/23/2013 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)

"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"

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"

In article ,
Sal salmonella@food poisoning.org wrote:

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.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Dave Platt" wrote in message
news
In article ,
Sal salmonella@food poisoning.org wrote:

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.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.


Wow! Thanks for such a clear explanantion. As I was constructing
my DE, with its gamma match, I didn't have much trouble getting a
decent match; What you say makes me sure that adding parasitic
elements will alter that match ... but the close-in first-director will
mitigate the problem. (I do plan to try the T-match; the gamma
match seems to be like ol' Rodney Dangerfield: No Respect.)

I have no shame in saying that this is my first beam, unless you
count the cookbook 20m 2-element quad for last year's Field Day.
On the flip side, I take pride in tackling everything new, especially
with the support of those who've scouted the road ahead for me.

Thanks again.

"Sal"

On 2/26/2013 3:57 PM, Dave Platt wrote:
In article ,
Sal salmonella@food poisoning.org wrote:

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.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.


Some of us old time EME/weak_signal builders call the first 4 elements
the K1FO launcher.

I did a lot of optimization over the last 25 years, but I didn't change
the first 4 elements of his design much. He got it right and it worked
especially well with a T match.

tom
K0TAR