For mobile work on AO27, SO50, AO51 a 2 metre quarter wave whip is all you need... to work the LEO's mobile and the satellite is 15 degrees or more above the horizon,
Absolutely, For a 19.5" whip in center of roof:
1) Has 5 dBi gain above 20 deg on 2m 2) Has 7+ dBi gain above 30 deg on 70cm 3) Is an omni 4) does not sacrifice 3 dB for circular 5) Above 25 deg, satellite is 6 to 10 dB closer! 6) works the birds solid for the center of high passes 7) Simplicity at its best!
Read about it: www.aprs.org/rotator1.html
Disadvantage: The only disadvantage is TIME. On the above web page you can also see that satellites spend 70% of their daily pass times below 25 degrees. BUT! For those best passes in the morning and the evening (or whenever) you can make solid contacts while mobile for about 5 minutes.
Also note, that you do NOT need any tracking program to predict passes. AO51 schdule repeats evry 5 days for example. Just write down the CENTER pass of the morning and evening for each day for 5 days. Update those 10 times on a small 3/5" card on the dash about once a month or so will predict all passes whenever you are mobile. There will be a pass 100 minutes earlier and 100 minutes later each day too. So you can predict all 6 passes a day from those same 10 times.
See how: www.aprs.org/MobileLEOtracking.html
Bob, WB4APR
When I used to do a lot of driving for work I used to use a 1/4 wave, and a high gain vertical antenna to work the birds. I would switch between the high gain when the bird was coming up to the 1/4 wave when it was up 15 degrees or so. Then back to the high gain vertical when it was getting back down below 15 degrees or so. Another good trick was to use the 1/4 for TX only, and listen with 1/2 of an Arrow (with pre-amp) for the 70cm, D/L out the drivers window, this would give you near armchair copy, when pulled over of course !
73 Jeff kb2m
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Bob Bruninga Sent: Saturday, May 30, 2009 8:19 AM To: mikehooles; amsat-bb@amsat.org Subject: [amsat-bb] Re: Re eggbeater performance - mobile
For mobile work on AO27, SO50, AO51 a 2 metre quarter wave whip is all you need... to work the LEO's mobile and the satellite is 15 degrees or more above the horizon,
Absolutely, For a 19.5" whip in center of roof:
1) Has 5 dBi gain above 20 deg on 2m 2) Has 7+ dBi gain above 30 deg on 70cm 3) Is an omni 4) does not sacrifice 3 dB for circular 5) Above 25 deg, satellite is 6 to 10 dB closer! 6) works the birds solid for the center of high passes 7) Simplicity at its best!
Read about it: www.aprs.org/rotator1.html
Disadvantage: The only disadvantage is TIME. On the above web page you can also see that satellites spend 70% of their daily pass times below 25 degrees. BUT! For those best passes in the morning and the evening (or whenever) you can make solid contacts while mobile for about 5 minutes.
Also note, that you do NOT need any tracking program to predict passes. AO51 schdule repeats evry 5 days for example. Just write down the CENTER pass of the morning and evening for each day for 5 days. Update those 10 times on a small 3/5" card on the dash about once a month or so will predict all passes whenever you are mobile. There will be a pass 100 minutes earlier and 100 minutes later each day too. So you can predict all 6 passes a day from those same 10 times.
See how: www.aprs.org/MobileLEOtracking.html
Bob, WB4APR
At 04:19 AM 5/30/2009, Bob Bruninga wrote:
For mobile work on AO27, SO50, AO51 a 2 metre quarter wave whip is all you need... to work the LEO's mobile and the satellite is 15 degrees or more above the horizon,
Absolutely, For a 19.5" whip in center of roof:
- Has 5 dBi gain above 20 deg on 2m
- Has 7+ dBi gain above 30 deg on 70cm
- Is an omni
- does not sacrifice 3 dB for circular
- Above 25 deg, satellite is 6 to 10 dB closer!
- works the birds solid for the center of high passes
- Simplicity at its best!
Read about it: www.aprs.org/rotator1.html
Disadvantage: The only disadvantage is TIME. On the above web page you can also see that satellites spend 70% of their daily pass times below 25 degrees. BUT! For those best passes in the morning and the evening (or whenever) you can make solid contacts while mobile for about 5 minutes.
Also note, that you do NOT need any tracking program to predict passes. AO51 schdule repeats evry 5 days for example. Just write down the CENTER pass of the morning and evening for each day for 5 days. Update those 10 times on a small 3/5" card on the dash about once a month or so will predict all passes whenever you are mobile. There will be a pass 100 minutes earlier and 100 minutes later each day too. So you can predict all 6 passes a day from those same 10 times.
See how: www.aprs.org/MobileLEOtracking.html
Bob, WB4APR
I've posted this before, but maybe it helps to repeat. When AO-51 launched, I used a 19-inch mag-mount mobile whip on a steel ground plane to copy telemetry on 435-MHz using a preamp. Signals were quite adequate. Probably low horizon AOS/LOS was limited (too long ago to remember). But very simple to implement and use as Bob states. I have two Lindenblad antennas under construction so will play with them (using my 435 preamp) when I get them up. I am preoccupied with finishing my 1296-eme station with 16-foot dish. In July, I should be able to re-assemble the old AO-40 tracking super-array of antenna as can be seen on my website.
*********************************************************** 73, Ed - KL7UW BP40iq, 6m - 3cm 144-EME: FT-847, mgf-1801, 4x-xp20, 8877-600w 1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60/300W (not QRV) http://www.kl7uw.com AK VHF-Up Group NA Rep. for DUBUS: dubususa@hotmail.com ***********************************************************
Bob, It also has a null on an overhead pass.
Art, KC6UQH.
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Bob Bruninga Sent: Saturday, May 30, 2009 5:19 AM To: mikehooles; amsat-bb@amsat.org Subject: [amsat-bb] Re: Re eggbeater performance - mobile
For mobile work on AO27, SO50, AO51 a 2 metre quarter wave whip is all you need... to work the LEO's mobile and the satellite is 15 degrees or more above the horizon,
Absolutely, For a 19.5" whip in center of roof:
1) Has 5 dBi gain above 20 deg on 2m 2) Has 7+ dBi gain above 30 deg on 70cm 3) Is an omni 4) does not sacrifice 3 dB for circular 5) Above 25 deg, satellite is 6 to 10 dB closer! 6) works the birds solid for the center of high passes 7) Simplicity at its best!
Read about it: www.aprs.org/rotator1.html
Disadvantage: The only disadvantage is TIME. On the above web page you can also see that satellites spend 70% of their daily pass times below 25 degrees. BUT! For those best passes in the morning and the evening (or whenever) you can make solid contacts while mobile for about 5 minutes.
Also note, that you do NOT need any tracking program to predict passes. AO51 schdule repeats evry 5 days for example. Just write down the CENTER pass of the morning and evening for each day for 5 days. Update those 10 times on a small 3/5" card on the dash about once a month or so will predict all passes whenever you are mobile. There will be a pass 100 minutes earlier and 100 minutes later each day too. So you can predict all 6 passes a day from those same 10 times.
See how: www.aprs.org/MobileLEOtracking.html
Bob, WB4APR _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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On May 30, 2009, at 6:19 AM, Bob Bruninga wrote:
Absolutely, For a 19.5" whip in center of roof:
- Has 5 dBi gain above 20 deg on 2m
- Has 7+ dBi gain above 30 deg on 70cm
- Is an omni
- does not sacrifice 3 dB for circular
- Above 25 deg, satellite is 6 to 10 dB closer!
- works the birds solid for the center of high passes
- Simplicity at its best!
As an "aside" to Bob's comments, the higher takeoff angle of a 1/4 wave on 2m or 70cm is something that astute FM/repeater users in the mountainous areas of the country have always known... when you're at the bottom of a canyon, and the station/repeater you want to work is a couple of canyons over... a 1/4 wave will work because it'll get the signal "up and out" of the terrain via bouncing off rock walls, better than higher gain antennas. Everyone should have a basic 1/4 wave antenna available for their mobile station, for use in certain situations.
-- Nate Duehr nate@natetech.com
participants (5)
-
Art McBride -
Bob Bruninga -
Edward Cole -
jeff kb2m -
Nate Duehr