VHF Corner Reflector Antenna

[trooperdude]

I'm looking for plans or a source for a VHF corner reflector.

151 Mhz to about 160 Mhz

From my location on the East slope of the Santa Cruz mountains, I have a pretty good shot at most of the fire repeaters in the Western Sierra.

A yagi is a little too directional, so I'm looking for something like a
corner reflector to null out the back side and concentrate signal capture
east toward the Sierras.

Any suggestions ?

 

[zz0468]

You could try some of the ARRL books. They used to have stuff on corner reflectors. Have fun! A corner reflector on VHF can be pretty huge.

 

[k8mcn]

homebrew http://www.northcountryradio.com/Articles/crfl.htm

purchase http://www.arrowantennas.com/cb450.html


good luck

 

[trooperdude]

homebrew http://www.northcountryradio.com/Articles/crfl.htm

purchase http://www.arrowantennas.com/cb450.html


good luck

Thanks, the Arrow 2 meter looks like what I need.

I don't think I want to try homebrew for VHF.

 

[prcguy]

Most corner reflectors are targeted for about 10dB gain and take up more overall space than an equivalent gain Yagi. You don’t see to many VHF corner reflectors because they are huge!
prcguy

 

[trooperdude]

Most corner reflectors are targeted for about 10dB gain and take up more overall space than an equivalent gain Yagi. You don’t see to many VHF corner reflectors because they are huge!
prcguy

Yes, I know.

I have a VHF yagi for local fireground tactical comms, but the corner reflector seems to have a much wider fresnel capture area, which is what I need.

I'm not so concerned about the gain as I am about nulling out the backside (strong transmitter) and capturing a wider fresnel area for the Sierras.

 

[zz0468]

I've used corner reflectors as tx antennas in VHF simulcast systems because of the pattern and f/b ratio. Sometimes they're just what's needed, huge or not.

 

[k5uss]

Trooper,

A Yagi may still fit the bill and be MUCH easier to build. The more directors and the longer the spacing of a Yagi will tend to give you a much tighter "beam width". You might try modeling a 3 or 4 element Yagi with tighter spacing for the frequencies you want in "YAGIMAX". Do a Google for it, it's free and pretty easy to use. The shorter spacing and less directors may get you what you want with just some PVC pipe and brazing rod. A corner reflector is going to entail MUCH more than that for sure.

Since you are only monitoring with this antenna you can be off a little bit on the measurements and still get the forward gain with the rear and side rejection you want.

 

[DPD1]

Yes, I know.

I have a VHF yagi for local fireground tactical comms, but the corner reflector seems to have a much wider fresnel capture area, which is what I need.

I'm not so concerned about the gain as I am about nulling out the backside (strong transmitter) and capturing a wider fresnel area for the Sierras.

If half your plan is trying to get rid of something coming from behind you, then yeah, that's probably your best bet. Just not the kind of thing that neighbors love though. I saw one in use on a local rail line through a valley the other day. I'm kind of curious what their specific situation was that they needed it.

Dave
www.DPDProductions.com
Custom Antennas & Radio Accessories

 

[trooperdude]

Thanks for the replies.

With personal time constraints, I'd MUCH rather buy than build.

My problem is a 250 watt ERP simulcast system with one of the transmitters in the
hills directly behind me on 154Mhz at 680 meters asl.

My targets in the Sierra foothills are 151 Mhz CalFire repeaters, and 167Mhz US Forest
Service Repeaters. I don't expect to hear everything, but a good chunk I can already
receive on a scantenna at 30 feet.

When the local FD system transmits, it wipes out almost everything within 10 mhz of either side with desense, so my RX plan is a commercial radio and a corner reflector.

I'm still concerned that the Yagi will concentrate the beamwidth in too small of an arc.

I need something that has about a 70-90 degree arc, more or less, with a large null on
the back side.

I'm still noodling out the best solution, and typing out loud here for input.

If I can get a decent signal, I'll probably offer it up as a live internet audio stream
during fire season.

 

[DPD1]

That sounds like a pretty heavy duty signal to null. Is there something physical on the house you could use? Put the chimney behind it or something?

Dave
www.DPDProductions.com
Custom Antennas & Radio Accessories

 

[trooperdude]

That sounds like a pretty heavy duty signal to null. Is there something physical on the house you could use? Put the chimney behind it or something?
Dave

Unfortunately no. It's not solid.

With the transmitter altitude and ERP of the signal, even the 2 story houses in line with it do not affect signal strength.

I'm in RF hell actually, as I also have a high-power VHF paging transmitter site co-located on the top of an office building a mile away. A par filter took care of that and another one for the FM broadcast band desense.

I may have to get some pass-reject bottles to notch out the offending transmitter completely.

I think I'll try the $150 solution before I try the $1500 solution however.

It's only a hobby right ?? LOL

 

[kb2vxa]

Hi Troop and all,

To put it simply and keep it short, for a number of reasons a 2M Yagi can be tuned (more or less) into VHF Hi Band without modification and mounted vertically it's not as narrow as many think. It has four pretty decent corner lobes whereas when horizontal they practically disappear but you want vertical and not too directional so go for it. BTW, forward gain and front to back ratio remain unchanged so there's two specs you can count on.

 

[trooperdude]

Hi Troop and all,

To put it simply and keep it short, for a number of reasons a 2M Yagi can be tuned (more or less) into VHF Hi Band without modification and mounted vertically it's not as narrow as many think. It has four pretty decent corner lobes whereas when horizontal they practically disappear but you want vertical and not too directional so go for it. BTW, forward gain and front to back ratio remain unchanged so there's two specs you can count on.

My current vhf yagi is fixed and vertical, so I'll have to climb up on the garage this weekend and re-orient it towards Lake Tahoe and see what I can pick up.

If it works I'll just pick up another vhf yagi for the dedicated radio for this experiment.

The birds already love me.

Thanks all.