Trivec Avant Antenna

[blantonl]

I received my Trivec Avant portable Satcom antenna in the mail today - makes a whole world of difference in reception.

One thing is for certain - there are a ton of pirates using the CONUS UFO satellite. Wow!

I also caught some aircraft traffic on 261.575 giving a status report but didn't copy the whole exchange because my wife was complaining about the black antenna in the back yard.

Many more logs to follow!

 

[brandon]

Nice antenna! They are wonderful -- I consider them works of art. Is that 2040 one of those that were on eBay this past week? Saw a few priced very low and almost bought one.

Re the 261.575 traffic, it may have been Casino 1 that you heard?

 

[blantonl]

With this said - does anyone know of a good resource for determining the azimuth and elevation information so I can properly point the antenna?? I've used LIVE REAL TIME SATELLITE TRACKING AND PREDICTIONS before but it doesn't seem to have data for the UFO/Fltsatcom satellites

 

[blantonl]

Nice antenna! They are wonderful -- I consider them works of art. Is that 2040 one of those that were on eBay this past week? Saw a few priced very low and almost bought one.

Re the 261.575 traffic, it may have been Casino 1 that you heard?

Yes, it is a 2040 - a very well engineered antenna. Someone really did their homework in designing this antenna.

I'm not sure who I caught - sounded airborne though and there was a lot of VINSON voice in return to the unit.

Yes, I picked it up on ebay earlier this week for like $300 which I thought was a steal. And it is in almost brand new condition. It came from Fayetteville NC, so I wonder if it saw some special forces action? The carrying bag is pretty dirty and beat-up but the antenna itself is immaculate.

 

[krokus]

Nice antenna. I used the little brother of that model, while active duty.

 

[prcguy]

I toured the Trivec Avant factory years ago and asked if they or Dorne & Margolin came up with the folding element design and they admitted it was copied from the D&M C120 series. Otherwise Trivec makes good stuff.

I don't see the reflector deployed in the picture, I hope that's not the way its being used...
prcguy

Yes, it is a 2040 - a very well engineered antenna. Someone really did their homework in designing this antenna.

I'

 

[blantonl]

Yea, I forgot to deploy the reflector just before taking the picture. Reflector is deployed...

 

[blantonl]

Here is something interesting - I get far better reception on this antenna with the bottom reflector stowed and not deployed. Any ideas on why that might be the case?

 

[kb5udf]

Refletor and reception

I'll take a poke at this. I suspect that if not deploying the reflector elements improves your reception
it would suggest that the antenna may not have been exactly pointed in the right direction.
I would think that ordinarily having the reflector would improve the gain in a particular direction.
No reflector probably changes the pattern somehow, which should only help, assuming a well designed
antenna, if the aim was off.

JB

 

[blantonl]

Well, one thing to consider is that these antennas aren't entirely super directional for receive. I can get the same signal strength and reception varying the azimuth and elevation by at least 20 degrees in either direction.

Maybe the bottom reflector is for more transmit performance? But, as seen in the above picture, with the antenna deployed as you see I get the best reception.

 

[prcguy]

The Trivec and all similar antennas are two opposing dipoles about 1/4 wavelength over a ground plane and fed 90deg out of phase to create right hand circular polarity. The dipoles are actually configured for left hand polarity and the polarity reverses to right hand after bouncing off the reflector.

When you fold up the reflector you are relying on the actual ground for the bounce and pol swap and if the antenna is sitting about 1/4 wave or multiples it will still respond to RHCP but other than the right height it will not and have some serious loss. The pattern may also be skewed without the reflector deployed.

A classic example of a UHF satcom antenna that is the wrong polarity without the ground plane is the round the world without refueling flight of the Voyager flown by Dick Rutan. I was told a simple UHF satcom cross dipole was built and embedded into the aircraft for use with an emergency satcom radio. The system apparently worked ok on the ground but as soon as it got airborne the UHF satcom radio would cease to work.

An antenna savy person finally discovered they had built a left hand pol antenna and when on the ground the ground bounce reversed the pol to the needed right hand but there was no ground bounce after the aircraft got airborne.

The solution which they flew the 1st round the world flight without stopping was to stuff a Trivec or D&M mil satcom antenna inside the aircraft and point it manually.
prcguy

 

[SCPD]

Lindsay are you using a preamp?

 

[Rt169Radio]

Definitely a interesting antenna design, are they only for SATCOM listening?

 

[mdulrich]

With this said - does anyone know of a good resource for determining the azimuth and elevation information so I can properly point the antenna??

I use Orbitron for ISS tracking and it works very well, including showing azimuth and elevation information and will do visibility predictions. You will need to find the TLE that has the information for the sats you are looking for. Satellite Tracking System: Orbitron by Sebastian Stoff / Satellite tracking easiest ever!

Mike

 

[prcguy]

Most models will cover the full 225-400MHz band and can be used for mil air, etc. Since they are circular polarity you will loose about 3dB when listening to a signal from a linear pol antenna so the 7dBic gain of a basic model without directors becomes about 4dBi gain or about 1.86dBD gain.
prcguy

Definitely a interesting antenna design, are they only for SATCOM listening?

 

[prcguy]

For geostationary sats like UHF its much easier to use this:
Satellite Finder / Dish Alignment Calculator with Google Maps | DishPointer.com
prcguy

I use Orbitron for ISS tracking and it works very well, including showing azimuth and elevation information and will do visibility predictions. You will need to find the TLE that has the information for the sats you are looking for. Satellite Tracking System: Orbitron by Sebastian Stoff / Satellite tracking easiest ever!

Mike

 

[Your_account]

what is an good deal for (a used) Antenna?

 

[brandon]

Here is what they have been going for lately on eBay. Prices seem to be cheaper now than they were a few years ago.

 

[Your_account]

How about that:
TRIVEC-AVANT UHF SATCOM ANTENNA UHF P/N AV 2040-2 | eBay
the seller look a little bit ....

 

[Your_account]

Hey i found a great and cheap offer can someone look at it and check the condition of the antenna?
THX!!