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Old Dec 15, 2011, 04:29 PM
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Let me just drop in here and ask a question.

I know what an SWR meter is. What are you using it for as it relates to RC radios?
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Old Dec 15, 2011, 04:33 PM
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Quote:
Originally Posted by UlteriorModem View Post
Let me just drop in here and ask a question.

I know what an SWR meter is. What are you using it for as it relates to RC radios?
To tune and test our homebuilt FPV antennas
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Old Dec 15, 2011, 06:46 PM
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I posted, in a previous thread of IBCrazy's, a DIY 900MHz - 2.5GHz set-up.

http://www.rcgroups.com/forums/showt...3#post17981418

Regards,

Eusebio

I think it might be possible to use a surface mount mini-circuits bi-directional coupler like the SYBD-13-63HP+ for 5.8GHz but I've never used one of these before. The price is right at 29 bucks plus shipping. Can one solder RG-174 directly to the chip?
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Old Dec 15, 2011, 09:15 PM
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Quote:
Originally Posted by ek123 View Post
I posted, in a previous thread of IBCrazy's, a DIY 900MHz - 2.5GHz set-up.

http://www.rcgroups.com/forums/showt...3#post17981418

Regards,

Eusebio

I think it might be possible to use a surface mount mini-circuits bi-directional coupler like the SYBD-13-63HP+ for 5.8GHz but I've never used one of these before. The price is right at 29 bucks plus shipping. Can one solder RG-174 directly to the chip?
I don't see why not. Try it.

-Alex
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Old Dec 16, 2011, 07:02 AM
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USA, NY, Bellmore
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How timely!
I just made a dual band VHF - UHF antenna for the shack and with only a SWR bridge for VHF I had no way of checking it at 450! Do now.
Great Christmas present!
Thanks!
Rudi
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Old Dec 16, 2011, 10:23 AM
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New York
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Quote:
Originally Posted by n5iln View Post
SMD directional couplers can be had from Mouser for under USD3
do you have a link for that? id like to build this swr meter but i couldnt find anything by that description.
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Old Dec 16, 2011, 10:43 AM
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Search for DC4759J5020AHF, for 5.8GHz. 60 cents !!!
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Old Dec 16, 2011, 11:23 AM
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thank you renato, as usual you are one of the most helpful people on rcgroups.

there are 4 freq ranges so i ordered a couple of each. looks like they will handle 900mhz-5.8ghz and everything in between. im still not quite sure why some cost $29 or even hundreds of dollars when these are so cheap.
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Old Dec 16, 2011, 11:25 AM
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Likely because not everyone is skilled at or comfortable with working on SMDs, so they wait for someone to pre-package it in a nice housing and add all the connectors for them. Presto: instant 400% markup (or more!).
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Old Dec 16, 2011, 11:31 AM
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New York
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or 4,000% markup! its hard to believe.

heres the spec sheet in case anybody else is interested. since alex's circuit is virtually identical to the one in my rf field strength thread and the diode there is also cheap and works up to 5.8ghz im hoping i can build one of these with the same parts.
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Old Dec 16, 2011, 05:58 PM
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Yes, it seems to be quite a mark-up but the mini-circuits coupler is bi-directional and has a much greater bandwidth (probably neither of these factors is important for the application we have in mind). I did notice that mini-circuits has a narrow bandwidth bi-directional coupler chip for $2 (MBD-20-63HP+) but I think the shipping is very expensive (something like 11 dollars last time I ordered--even something small and lightweight). There is also an evaluation board to mount the chip and some SMA connectors but I couldn't find a price (found it, $35).

Eusebio
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Old Dec 21, 2011, 07:36 AM
RC beginner
New York
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fyi 1n5711 high frequency schottky diodes available from digi-key for 50 cents each:

http://parts.digikey.com/1/parts/413...35-1n5711.html

minimum order was $25 so i offered to sell the extras at 1$ ea shipped. anybody interested pm me their shipping address.
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Old Dec 21, 2011, 07:40 AM
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Ebay, guys. That's how you get around the minimum order price Lots of electronic goodies can be found there.
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Old Dec 21, 2011, 10:14 AM
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New York
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the couplers arrived and ill start construction soon. they are much smaller than i anticipated so it will be a real challenge soldering those up. my coax is way too thick so it looks like i may have to sacrifice one of the frsky antennas just to get some thin enough. im wondering how critical layout is. probably pretty tricky considering 2.4ghz.

ps i checked ebay and unfortunately nobody is selling small quantities (unless you count the guy who wants $8 qty 1! ). if you have use for 50 or so there might be an advantage but for those who just want to buld a field strength meter or swr meter i dont think you can beat a buck shipped anywhere.
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Old Dec 22, 2011, 12:11 PM
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Mini-circuits directional coupler on eBay

Hi,
Here are two cheap couplers found on eBay:

Mini-Circuits ZADC-10-17W 10dB Directional Coupler
http://www.ebay.com/itm/ws/eBayISAPI...m=350510321526


Mini-Circuits RF Power Coupler 2GHz 13dB SMA ZADC-13 x1
http://cgi.ebay.com/ws/eBayISAPI.dll...m=310209833363

Are they ok to build an SWR meter in the 900Mhz-1.3Ghz range ?
Thanks !
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