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 Subject :BDAs with Long Coax Run Solution?.. 2016-11-18- 15:21:30 
Joined: 2016-11-17- 23:26:03
Posts: 11

Greetings, all!

I'm just starting to get into HSMM-MESH, and am loving it.  Admittedly, I've got zero experience with GHz frequencies, but the study is fascinating.

Just flashed about four WRT-54G's with great success.  Oh my goodness, is this an eye-opening and devastatingly cool use of older technology.

Come enter my brain for a sec...I need to know if bi-directional amplifiers (BDA's) would prove to be at all useful with long runs of LMR-400.  The story is, I've got a cemented 8' pole out back that I was originally going to use with an HF antenna.  Sadly, it didn't work out, and opted for a vertical for the moment.  However, I was thinking:  could there exist a potential opportunity to use this pole to mount a 24dBi parabolic WiFi antenna to use with a newly flashed HSMM-MESH router?  The game is afoot!

Here's the sad reality:  the LMR-400 run is 140'.  At first blush, I said forget it.  However, I've been reading about bi-directional WiFi amplifiers and started wondering.  My question is:  would there be any hope of using my 140' run of LMR-400 coax with one of my flashed WRT-54G's (with a 24 dBi parabolic)?  Would a BDA (or some other solution) make this dream a reality?

Please go easy on me, as I tend to be more of a dreamer than anything.  (LOL!)  If BDA's won't do the trick, is there something reasonably-priced that would work?

Thank you, thank you, thank you for reading this post, and dreaming-a-little-dream with me.  :)

Cheers, blessings, and 73s!


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 Subject :Re:BDAs with Long Coax Run Solution?.. 2016-11-25- 14:33:42 
Joined: 2012-03-06- 08:19:44
Posts: 39
Location: Cottonwood, AZ
I guess nobody has answered this yet? I'm surprised, this site used to be way more active. Well, here's an idea... forget the 140 ft of LMR and use twinlead wire that will provide 12-15 volts DC to your node at the top of your pole, tower, or wherever you want to put your dish. Put your node up there. Then, get a second node and set that up 140 feet away on the ground some place and let the two chat. It'll work fine but you will have some delay between units. Another solution I have adopted in my networks is get Cat5 ethernet cable, 8 conductors, use 4 wires for an ethernet connection to a DTD port on your remote node, and the other 4 wires for DC supplying that remote node. I put a 100uf capacitor across the dc line at the remote end also. An ordinary wall wart DC supply on the ground is all you need to power that remote node. Then connect the 4 wire ethernet half of the cable near end to another node that you've also set up as DTD port. Now you have very little delay and full control of the remote node as well. Not well known is that you can use a crossover cable ( Orange ethernet cable) to connect DTD nodes together BUT.... and this is important... if you reboot one - the other will hang. The workaround is to disconnect the cable while either node is rebooting for any reason. To avoid this inconvenience use a simple ethernet switch that's always powered up and connect both remote and local node to that switch. That's the more well know solution for pairing Tunneling Servers and Clients. It's well documented here in other messages. 73 - Wil - AB9U.
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de Wil - AB9U
 Subject :Re:BDAs with Long Coax Run Solution?.. 2017-01-21- 22:25:09 
Joined: 2013-05-30- 13:18:20
Posts: 2
Well, the big thing as I see it is that in that 140' run of LMR-400 is that the loss will be 9.24dB. This means you will have about 1/8 of the power availible at the antenna...Not so good. I would like to see 6' or less of LMR400. Regards, Phil KK6PE
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