Mk4 Sniffer with Arrow II Yagi

Started by Jerry Jacobs, April 10, 2012, 04:29:39 AM

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Jerry Jacobs

April 10, 2012, 04:29:39 AM
My squadron is looking into getting a Mk4 to replace our aging L-Per's and it seems the best antenna for the receiver is a matched antenna from http://www.arrowantennas.com/arrowii/arrowii.html with shipping between the Mk4 and antenna should be around $300 which is well within reach of my squadron. The one thing I am concerned about this antenna is how to mount the unit onto it. It seems here isn't enough of a gap between the handle and the reflector beam.

Has anyone else used this antenna with the Mk4? How did you mount the unit onto the antenna? Does the antenna break down quickly? How do you store the antenna?

Also I came across http://www.backpacking.net/makegear/yagi-antenna/index.html as a possible homemade antenna solution but I don't think the elements of piano wire elements would be durable enough for Ground Team use.

What other antennas are people using with this receiver?

SarDragon

#1
April 10, 2012, 05:40:48 AM
That size piano wire is OK, but a size or two larger might be better. I've seen Yagis made with cut up measuring tape. They are easily stored, and are flexible enough to take the abuse of going through the woods.

Also, keep in mind that the dimensions on the linked page are not correct for 121.5 MHz. That antenna is centered on the Ham 2-meter band, around 147.5 MHz. Everything will be longer for 121.5 MHz.
Dave Bowles
Maj, CAP
AT1, USN Retired
55 Year Member
Mitchell Award (unnumbered)
C/WO, CAP, Ret

Major Lord

#2
April 10, 2012, 12:42:10 PM
Jerry,

Bob Miller, a CAP guy, is an RDF antenna god! (small G: no blasphemy intended!) He is also a distributor I believe for the MK IV. http://www.rdfantennas.com/bc121Antenna.htm His antenna is a folding three element Yagi cut and tuned specifically for 121.X, and he also make a ham radio "Fox hunt" version.

Its really not a good idea to mount the receiver to a Yagi antenna, especially between elements. It will detune your antenna. Also, the MK 4 is really great with a rubber duck whip as a close in unit when you are faced with the dreaded flight line full of C-172's and can't tell which one has the ELT!

Major Lord
"The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he, who in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy my brothers. And you will know my name is the Lord when I lay my vengeance upon thee."

Jerry Jacobs

#3
April 11, 2012, 01:48:14 AM
I did see Bob Millers website but this antenna is over $100 than what I'm looking at right now and he sells the Mk4 for $120 higher than it costs from the guy that makes the unit. Although that antenna is exactly what is needed I am willing to save the money by going with the Arrow antenna to hopefully use to buy more ES goodies. So how would you recommend holding the unit to the antenna is a way that doesn't affect the tuning too much?

SarDragon

#4
April 11, 2012, 02:32:39 AM
OK, now that I've taken the time to look at the antenna in question, I would recommend not attaching the two parts. Use a 2 or 2 ft section of RG-58 to connect them, and leave it at that. I have a buddy who used his Yagi with his L-per, and he can point the antenna wherever he wants, and still keep the receiver display at a comfortable viewing angle.
Dave Bowles
Maj, CAP
AT1, USN Retired
55 Year Member
Mitchell Award (unnumbered)
C/WO, CAP, Ret

Major Lord

#5
April 11, 2012, 03:42:43 PM
Sardragon,

Fully concur. Its nice to be able to change antenna polarization, hold it up over your head, etc. I would buy the MK IV from the Aussie, but would buy Bob's antenna over the Arrow.

Major Lord
"The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he, who in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy my brothers. And you will know my name is the Lord when I lay my vengeance upon thee."

starshippe

#6
April 12, 2012, 02:48:19 AM
   heres a pic of bob's antenna and the mk4. i can not tell the difference in antenna performance from having it mounted just aft of the active element. if u want, use a short piece of coax and mount it wherever u like. all u need to do is be able to hear it. a glance at the attenuation level every so often will tell u how close ur getting.

   the only change i have made is the addition of the washers in the screw slots so i don't have to find the screwdriver, that probably detunes the antenna some too.

   i also use the arrow antennas and the l tronics beam antenna with the mk4, and the l tronics.

   the advantage of the mk4 to me is the fact that it is synthesized and covers the ham band too.

   the advantage of the l tronics is the sensitiviey. its still the first box out of the back of the truck.

   i've been trying to get bryan, the aussie guy, interested in building one that would cover 406, but it hasn't made it to the front burner yet.

good luck,
bill

Ed Bos

#7
April 12, 2012, 05:31:01 AM
A gentleman on the MDWG ES Staff has a Sniffer with an excellent homemade antenna that only cost a few dollars. It's constructed from PVC piping and lengths of steel measuring tape.

I've had a chance to use it several times at NESA and it's terrific.

PM me if you'd like more details.
EDWARD A. BOS, Lt Col, CAP
Email: edward.bos(at)orwgcap.org
PCR-OR-001
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