Re: Frequency selection for airborne crossband repeaters

Bill Brown
 

I would go with the 500 mW setting since it will likely have a high duty cycle and could overheat, even at 500 mW it could still overheat so try to mount the module on a good heatsink. Since you are running ATV on 70cm, you will want to transmit the crossband repeater on 70cm as well otherwise the receiver will be desensed by ATV EMI hash. But be aware to keep good separation between the ATV payload and the crossband repeater since you could see interference from the ATV transmitter getting into the 2m receiver as well. Perhaps a low-pass filter or bandpass filter in front of the receiver module would be a good idea. Also be aware that the ATV transmitter and camera could desense GPS receivers so also keep separation between the ATV payload and your balloon trackers.

- Bill WB8ELK

I would agree with other posts on this topic that it is best to stay with simplex frequencies. That's why I always fly with 446.025 out and 144.340 input or vice versa. The 446.025 frequency is not used a lot as compared to 446.000...although 445.975 and 446.300 are good alternates. Same for 144.340. It is primarily used nation-wide as an ATV talk frequency and occasionally for APRS links for balloon flights. The ATV folks don't mind and love to follow balloon flights and particularly appropriate in this case since you are flying an ATV transmitter. Even if someone is using 144.340 and not following your balloon, it won't matter since you won't interfere with them. I did fly a crossband repeater years ago from 73 Magazine headquarters in NH with 446.000 as the input and a 25 milliwatt 10m FM transmitter as the output during the VHF/UHF contest. It was a blast hearing all the mountaintop rover stations from well beyond typical line-of-sight ranges. Yes, that's right I used 10m as the output. It is legal to do so in the FM portion of 10m.








From: Michael Hojnowski <kd2eat@...>
To: GPSL <GPSL@groups.io>
Sent: Wed, Feb 27, 2019 12:12 pm
Subject: Re: [GPSL] Frequency selection for airborne crossband repeaters

Well, I pulled the spreadsheet kept by the Upstate New York Repeater coordinators, and found a few frequencies that seem clear - 144.580 input, 447.025 output. 

I'm going to try a few NiceRF SA828 Walkie Talkie modules.  Not sure if I'll run them at 500mW or 1W.   Since it'll be transmitting on 70cm, I'm inclined to use the lower power, since it'll have lower free space path loss.  That would also reduce battery drain.

This is going to be an ambitious flight, including analog TV video on 70cm, the repeater, a payload drop initiated via DTMF tones, and with luck, the entire thing livestreamed onto youtube.  We hope to have a ground station with a high gain beam tracking based on APRS beacons, and feeding into the youtube stream.  

Bill / WB8ELK has me on the agenda to talk about the successes (or spectacular "lessons learned") at the Balloon Sat session at Dayton.

As the flight draws near, and we're confident we can livestream, I'll post URLs for those who would like to watch at home.  Tentative flight date is Sunday, April 28 with a rain date on May 5.

Mike / KD2EAT
Advisor, Amateur Radio Club at Cornell


On 2/27/2019 12:23 PM, Joe wrote:
I agree with Bill on that Pairing.

FORGET repeater co-coordinators. We used them on the very first repeater flight ever.Way back in like 1989 or so. And They just do not understand the coverages we can get with these flights. And one of the UHF freqs we were suggested to use as being safe, ended up being a UHF link from a repeater system, satellite receivers. So in the middle of our flight, suddenly on the balloon was a swapnet happening.

But if you want quiet great freq the pair Bill stated below we have used probably a dozen times and have worked great every time.

Now if you really want to have FUN! Many will make me now to put on my Flame suit. But we have done it probably 4 times? But the biggest fun was this pair
 146.52/446.000  Yup! It was crazy easily worked well over 300+ stations!

Mike what do you plan on usi9ng for equipment?

Will the repeater go both ways, think HT in crossband repeat but both directions.

Joe WB9SBD
KB9KHO
Near Space Sciences

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 2/27/2019 9:59 AM, Bill Brown via Groups.Io wrote:
I typically use 446.025 and 144.340. Both are simplex. For a simplex repeater i use 144.340. 
-Bill WB8ELK
On Feb 27, 2019, at 8:39 AM, Michael Hojnowski <kd2eat@...> wrote:

Hey Gang,

I'm intending to fly a cross-band repeater with a HAB in April.  It occurs to me that I don't have a good idea of how to select frequencies.  Should I be using one from the repeater input range on one band, and output on another?  Should I be selecting simplex frequencies for this short term use?  Should I attempt any kind of coordination with our regional frequency coordination groups?

What have people done?

Thanks for any advice,
Mike / KD2EAT





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