4 element yagi.

[Planeguysexploration]

I built this simple 4 element yagi from a tape measure and some PVC, made to get some EMS transmitters from the county over. Also wondering if I would be able to pick up any amateur satellites with it. (Obviously not transmit). Built for 425 megahertz.

 

[KB4MSZ]

Very clean construction. This yagi should have a feed impedance of about 25 to 35 ohms. If that is a 300 to 75 ohm (4 to 1) balun it may cause diminished performance. I would try feeding it directly.

 

[Planeguysexploration]

Very clean construction. This yagi should have a feed impedance of about 25 to 35 ohms. If that is a 300 to 75 ohm (4 to 1) balun it may cause diminished performance. I would try feeding it directly.

My radio has an impedance of 50 ohms, I'd need to buy another balum. I guess it would be more effective with a direct feed though.

 

[KB4MSZ]

75 Ohm is quite low loss and the miss-match isn't really much of a problem when just receiving. This is especially true if you are running a long length of coax, I would stick to the 75 ohm.

Lower impedance coax has better power handling capabilities but more loss. Higher impedance coax has lower power handling capabilities but less loss.

 

[vagrant]

Yes, you probably can RX satellite voice and data comms. Here is a web page that lists various FM satellites and their UHF downlink frequencies. Four of them are active and one of them is the ISS. There are definitely people using the repeater on the ISS when it is turned on.

KA7FVV - Amateur Satellite Information

You can use this webpage to identify and track those satellites to find out when you are in their respective footprint.

https://www.n2yo.com

 

[prcguy]

Get rid of the 300 ohm balun and go with a direct coax feed with the shortest leads from the coax to the elements. Then put three #43 mix snap on beads over the coax right at the feedpoint to act as a crude balun. No reason why you can't transmit on it and probably with 100 watts if the dimensions are right and the match is good.

 

[mmckenna]

I built a 460MHz version of that to do some interference hunting at work. I needed something quick and it was going to take to long to order one. Worked quite well, found the offender and resolved the issue. Easy to build and easy to tune. And thanks to Harbor Freight and their "free" tape measures, it was dirt cheap to build.

I used it for transmitting several times. The direct connection of coax is the way to go.

 

[Ubbe]

The balun will only operate as a 4:1 transformer and reduce the signal level 4 times. If you replace the 1/2 wave dipole with a folded one you get a more appropriate 300 ohm antenna that matches the baluns impedance. You can probably look at a TV antenna's folded dipole and scale up the size to something like 150%.

/Ubbe

 

[Planeguysexploration]

I think I'll split the coax, have to wait for the splitter to arrive.

 

[merlin]

Not shabby at all but as mentioned, I would go with RG58U directly. That should give you the gain the Yagi is noted for.
Receiving, this should give good results from 400 to 500 Mhz.
Transmitting should good within 10 Mhz of design frequency with decent SWR.

 

[Planeguysexploration]

I gave it a direct feed, works much better, thanks.

 

[Planeguysexploration]

I finally fixed the feed, (it broke)