Log periodic antenna
 

Does anyone have design for a log periodic antenna comparable to the
Elk one for 2 meters and 70 cm. I'd like to build one for satellite
work, and with the log periodic, I believe I could avoid the diplexer
issue.

Please respond directly to

Thanks!
/paul W3FIS

Log periodic antenna
 

On Aug 6, 7:06*pm, professorpaul wrote:
Does anyone have design for a log periodic antenna comparable to the
Elk one for 2 meters and 70 cm. I'd like to build one for satellite
work, and with the log periodic, I believe I could avoid the diplexer
issue.

Please respond directly to

Thanks!
/paul W3FIS

Actually, for a dual band to one feed, you can probably just
interleave the elements of a 2m and 70cm beam on the same boom and
connect the driven elements in parallel.

http://www.arrowantennas.com/ look at the model 146/437... they have
plans on the site to build it yourself. While they have a filter box
available, I'm not sure you actually need it.

Log periodic antenna
 

"professorpaul" wrote in message
...
Does anyone have design for a log periodic antenna comparable to the
Elk one for 2 meters and 70 cm. I'd like to build one for satellite
work, and with the log periodic, I believe I could avoid the diplexer
issue.

Please respond directly to

Thanks!
/paul W3FIS

Hi Paul

"For what it is worth", I support Jim Lux's advice. A 70 cm Yagii wont
couple much power from the transmitter when sending on 2.meters It would
be easy to test the effect of shunting the 435 receiving Yagii with the 2
meter Yagii. You could even do that with EZNEC.
An antenna like Jim suggests would be easy to build on a broom stick to
test the effects of the 'other antenna'.

The principal value of the Log Periodic is it's bandwidth. That is not
significant when only two discrete frequencies are considered. A
disadvantage of the Log Periodic is it's limited gain. I fail to see where
the Log Periodic benefits the user when only two frequencies are being
considered.

Jerry KD6JDJ

Log periodic antenna
 

On Fri, 07 Aug 2009 17:54:16 GMT, "Jerry"
wrote:


"professorpaul" wrote in message
...
Does anyone have design for a log periodic antenna comparable to the
Elk one for 2 meters and 70 cm. I'd like to build one for satellite
work, and with the log periodic, I believe I could avoid the diplexer
issue.

Please respond directly to

Thanks!
/paul W3FIS

Hi Paul

"For what it is worth", I support Jim Lux's advice. A 70 cm Yagii wont
couple much power from the transmitter when sending on 2.meters It would
be easy to test the effect of shunting the 435 receiving Yagii with the 2
meter Yagii. You could even do that with EZNEC.
An antenna like Jim suggests would be easy to build on a broom stick to
test the effects of the 'other antenna'.

The principal value of the Log Periodic is it's bandwidth. That is not
significant when only two discrete frequencies are considered. A
disadvantage of the Log Periodic is it's limited gain. I fail to see where
the Log Periodic benefits the user when only two frequencies are being
considered.

Jerry KD6JDJ


Mechanical and electrical precision.

A single frequency antenna must be tuned very carefully.
The LPDA is "self-adjusting" and easy to make.
And you may change frequency any time.

w.

Log periodic antenna
 

Helmut Wabnig wrote:
The LPDA is "self-adjusting" and easy to make.
And you may change frequency any time.

Question is: Why would an amateur radio operator
want to cover 148 MHz to 420 MHz with a transmitting
antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Log periodic antenna
 

"Helmut Wabnig" hwabnig@ .- --- -. dotat wrote in message
...
On Fri, 07 Aug 2009 17:54:16 GMT, "Jerry"
wrote:


"professorpaul" wrote in message
...
Does anyone have design for a log periodic antenna comparable to the
Elk one for 2 meters and 70 cm. I'd like to build one for satellite
work, and with the log periodic, I believe I could avoid the diplexer
issue.

Please respond directly to

Thanks!
/paul W3FIS

Hi Paul

"For what it is worth", I support Jim Lux's advice. A 70 cm Yagii wont
couple much power from the transmitter when sending on 2.meters It would
be easy to test the effect of shunting the 435 receiving Yagii with the 2
meter Yagii. You could even do that with EZNEC.
An antenna like Jim suggests would be easy to build on a broom stick to
test the effects of the 'other antenna'.

The principal value of the Log Periodic is it's bandwidth. That is not
significant when only two discrete frequencies are considered. A
disadvantage of the Log Periodic is it's limited gain. I fail to see
where
the Log Periodic benefits the user when only two frequencies are being
considered.

Jerry KD6JDJ


Mechanical and electrical precision.

A single frequency antenna must be tuned very carefully.
The LPDA is "self-adjusting" and easy to make.
And you may change frequency any time.

w.

Hi W

I hadnt realized that Yagiis were so difficult to build and tune. Have
you considered telling the AMSAT guys about how they can benefit from your
advice? It seems that most of the AMSAT guys have been using the "Arrows"
for LEO satellite work.

Jerry KD6JDJ

Log periodic antenna
 

On Aug 7, 5:03*pm, Cecil Moore wrote:
Helmut Wabnig wrote:
The LPDA is "self-adjusting" and easy to make.
And you may change frequency any time.

Question is: Why would an amateur radio operator
want to cover 148 MHz to 420 MHz with a transmitting
antenna?
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

I only want to cover 144 and 420, nothing in between! Just for LEO
satellites, where the uplink is on 144 and the downlink is 420, or vis
versa.

/paul W3FIS

Log periodic antenna
 

"professorpaul" wrote in message
...
On Aug 7, 5:03 pm, Cecil Moore wrote:
Helmut Wabnig wrote:
The LPDA is "self-adjusting" and easy to make.
And you may change frequency any time.

Question is: Why would an amateur radio operator
want to cover 148 MHz to 420 MHz with a transmitting
antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

I only want to cover 144 and 420, nothing in between! Just for LEO
satellites, where the uplink is on 144 and the downlink is 420, or vis
versa.

/paul W3FIS

Hi Paul

AO-51 is a good HAM satellite. It is 146 up and 435 down.
If you do want to get some good experience designing Log Periodic
antennas, you might consider a Log Periodic V. The V configuration takes
advantage of a three to one frequency spread, where a center fed 1/2 wave
dipole becomes 3/4 wave at 3 times the frequency. The low frequencie
pattern is little effected by the "V". The high frequencies (3 times the
low frequencies) appreciate the bending to the V because that allows the
sidelobes to add toward the "front".

Jerry KD6JDJ

Log periodic antenna
 

"professorpaul" wrote in message
...
I only want to cover 144 and 420, nothing in between! Just for LEO
satellites, where the uplink is on 144 and the downlink is 420, or vis
versa.

then forget all the complications of log periodics and just make 2 simple
yagis on the same boom. that is the common method of constructing
directional satellite antennas. same boom too complicated, just make 2
separate ones and mount them on a cross arm a few feet apart.

Log periodic antenna
 

professorpaul wrote:
On Aug 7, 5:03 pm, Cecil Moore wrote:
Question is: Why would an amateur radio operator
want to cover 148 MHz to 420 MHz with a transmitting
antenna?

I only want to cover 144 and 420, nothing in between! Just for LEO
satellites, where the uplink is on 144 and the downlink is 420, or vis
versa.

Then you would be wasting 98% of the frequency coverage
of the log periodic. The unused antenna elements would
constitute almost the total cost of the antenna.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com