Airband antenna: experience and suggestions?

[Marco192]

Hi guys!
I hope that you can help me with your experience in finding the best antenna for airband (vhf).
There are three options that seem feasible to me and I was wondering which option would give me the best possible results:
1. Diamond X510 (that is a HAM antenna with big gain on 144 mhz band)
2. a homemade 1/4 ground plane antenna
3. some sort of a discone antenna

Thanks for your help!

 

[vagrant]

Discone - It offers the bandwidth for VHF air, as there is a wide frequency spread to cover. These cost anywhere from $40 - $100 USD. Discone antennas can cost much more $600 - $2000, but not really worth it unless your weather environment is brutal with ice and or wind, or your uptime demanded a rock solid discone.

The Diamond or a DIY vertical will not provide the same amount of bandwidth as well as not being tuned for VHF air. If the vertical of the antenna was around 4 - 5 cm in diameter or more, then it should work out. There should be commercial versions of vertical antennas with this kind of diameter, but a discone can be purchased for much less. I use a discone for airband VHF as do private, public and military facilities.

- The higher the better for antenna placement.
- Use quality coaxial cable and as short a run as possible.
- One can add a filter and or amplifier later to clean things up and or provide a boost. Try a filter before an amplifier first, as the amplifier may make the issue worse by boosting an unwanted signal. See this thread below for FM broadcast filter options.

FM bandstop filter comparison

I rolled some numbers on the RTL-SDR FM bandstop filter and the HPN-30118 AM/FM filter using a VNA. The results are interesting compared to the ZBSF-95+, especially when you hit VHF Air voice at 118 - 137 MHz. The ZBSF-95+ numbers come from their spec PDF as I do not own that yet. There are...

forums.radioreference.com

 

[Ubbe]

I first had a 1/4 GP antenna cut for 125Mhz then modified a AIS marin 5/8 GP antenna from Sirio by changing the element to a longer one and that gave a better reception. My X510 was poor in comparison in VHF air. The schematic for X510 looks a bit strange with a 1pF coupling capacitor in the middle of the antenna and the bottom coil for SWR matching looks like it might reduce the signal level. I soldered a jumper over that capacitor and moved the tap on the coil so that I got the whole signal to the coax and also removed a level reducing capacitor net between coil and coax.

After the modifications the antenna came to life and received with signal levels in all frequency bands that now seemed more in line with the size of the antenna compared to other antennas I have and VHF air where same or better than the 5/8 GP.

The X510 are a beast and I have a 2 ft PVC plastic tube to support it half way up to a parallell mast pole. I use an inner tube from a cycle tire inside the plastic tube that goes around the antenna as you want no metal near it and I knot the two ends of the cut off rubber tube around the mast pole.

My X510 cost me $150 and the marin antenna came free with a AIS receiver but probably costs $100 and their performance in VHF air are about the same in a modified state. The 6ft marin antenna are much easier to install but the 17ft X510 are a much better overall antenna to receive most frequencies between 25MHz-470MHz, after the modifications. I have no experiance of monitoring above 470MHz. A 1/4 GP will probably outperform a discone but if you also need to monitor UHF air and a lot of other general scanner frequencies, then a discone might be the best solution if you only want to use one single antenna for all monitoring you do.

Don't forget about using low noise amplifiers, as those has less internal noise than the scanner it will be like using an antenna that gives twice the signal 3dB, if you properly attenuate the signal at the scanner to not overload it that will make it receive worse than without the amplifier. And FM trapfilters are often neccesary at VHF frequencies to help the receiver from overloading, that also can happen to the amplifier if you are too close to a broadcast transmitter. If you only monitor VHF air with the antenna I would suggest a bandpass filter for 118MHz-137MHz between antenna and amplifier.

/Ubbe

 

[iMONITOR]

1. Diamond X510 (that is a HAM antenna with big gain on 144 mhz band)

Why not buy an antenna that is actually designed for airband reception? A Diamond X510 seems like a poor choice for aircraft.

 

[prcguy]

The Discone is a good recommendation and since the OP is in EU he might be able to get a Sirio broad band ground plane for a good price.
Look here for the model GP 108-136 LB-N GP- LB series

Hi guys!
I hope that you can help me with your experience in finding the best antenna for airband (vhf).
There are three options that seem feasible to me and I was wondering which option would give me the best possible results:
1. Diamond X510 (that is a HAM antenna with big gain on 144 mhz band)
2. a homemade 1/4 ground plane antenna
3. some sort of a discone antenna

Thanks for your help!

 

[popnokick]

Airband antennas addressed at length in this thread in the AirCraft Monitoring Forum (including a couple not mentioned at all in this thread here in Scanner / Receiver Antennas) -
Antenna for Military and Civilian Air

 

[AI7PM]

Discone. It'll give you good coverage on both VHF and UHF bands. I've been using them for this for 30 years. I used to hear the space shuttle on UHF 700 miles out.

 

[questnz]

As discussed on another forum with link above, Air tuned Air Omni UHF/VHF Base Antenna
excellent construction made in US of A

 

[Marco192]

Thanks a lot to everyone for great advice and info!

 

[majoco]

Quote from Air Omni UHF/VHF Base Antenna web page...

Weather Resistant: All fasteners are stainless steel ........ The antenna is constructed of 1 1/2" aluminum tube

Obvious;y they haven't read this...

Stainless Steel & Aluminum: Why You Shouldn't Use Them Together

Why Can’t You Use Stainless Steel and Aluminium Together? What is Galvanic Erosion, how it works and, how to stop it? Read More...

www.albanycountyfasteners.com

...and from lots of other sites - and common aircraft practice.

 

[questnz]

Martin, It could right on large scale of things but I don't think its a big issue here, only SS screws included are for holding whole thing and elements in place together, 6-8 screws total. What you would advice to use? Then the whole aluminum assembly is screwed to galvanized mast with galvanized u bolts. Actually it is my antenna is on the picture in above post by popnokick.
Agree "best practice" should applied in critical situations, craiky personally I think it is an OK. Dave from DPD been making quality antennas for sometime, no complaints. But thank you for bringing this info to discussion. Happy New year in Palmy.

 

[jonwienke]

A coat of non-conductive paint will prevent the galvanic problem, at least until the paint peels.

 

[KenMaltz]

I've been using a Diamond D-130-J discone for about 20 years here on Long Island. Does an excellent job from low to high end VHF Air. No problems with corrosion...still looks like new.

 

[xms3200]

I bought a Sirio WY 108-3N 108-137 MHz 3 Elements Yagi Antenna....this antenna is outstanding. It is strictly for VHF airband, 118 - 136 Mhz which is what I listen to exclusively. If you want "awesome" performance on this band. look no further.