Rabbit ears for 2 meter?

[joseph2020]

First, let me establish, I am extremely strapped for cash and need cheap solutions for a very expensive hobby.

I saw the plans (I am enclosing the link) for a 2 meter antenna made from a old school TV rabbit ears. Has anyone ever heard of or used such a thing?

take a look:
Homebrew 2 meter Amateur Radio Antenna from Ordinary TV Rabbit Ears antenna » Please Name My Blog

Think it would work? Thanks in advance

 

[Murstech]

Sure.. That will work. You could even substitute regular old speaker wire in place of the telescoping elements and create an antenna for pennies. The elements are going to be about 20 inches long.

 

[joseph2020]

Murstech, thanks for your reply. It looks to me like a regular dipole with easy adjustable freq match via the adjustable "ears". The speaker wire idea is good, I thought about that (I have the wire) ...but decided against it.

The "ears" idea is a nice for tuning, and in a neat packaqe. No loose wire hanging about. It's either that or a home brew idea for a J pole antenna using 300 ohm twinlead , rg-58, and a balun or ferrite bead (need this part). thanks again

Any further ideas on the "rabbit ears" antenna are welcome.

 

[ampulman]

I made the offset center fed dipole from rabbit ears. Works great.

It would not open fully 180 degrees, so I filed the (inside) 'stops' to enable that. The long arm is a few inches short of 48, but it doesn't seem to matter.

Are you planning on using a TV adapter or directly connecting your coax?

Amp

 

[joseph2020]

ampulman, Fantastic Reply! YOU actually used one?

It would not open fully 180 degrees, so I filed the (inside) 'stops' to enable that. The long arm is a few inches short of 48, but it doesn't seem to matter.

what about trying as a "inverted V" dipole using the "ears"?

Are you planning on using a TV adapter or directly connecting your coax?

I am looking for a 300 - 50 ohm converter now. I am hoping to make a good match that way.

Any information you want to send is welcome.

 

[LtDoc]

'Rabbit-ears' will work, and are certainly handy for some uses. Instead of using a balun to change impedances, and depending on how those 'ears' are made to start with, why not just change the feed line to 50 ohm coax? If you can get to the insides of the thing, it shouldn't be that difficult to do.
A couple of things to keep in mind. If/when you find the positioning for the best performance, mark it on the 'ears'! Helps re-finding that 'spot' if something changes (length/angles)? I'd also recommend not placing it on top of the radio. Moving it away from the radio (and you) is sort of a good idea.
- 'Doc

(Once used a 2 meter antenna 'drawn' on a long piece of paper with a carbon pencil (dipole). Hardest part was making 'connections' to the lines on the paper with the coax. It worked. Not well, but better than no antenna at all.)

 

[prcguy]

If you make the elements 19 to 20" long each the feed point impedance will be around 50 to 75ohms and you would feed it directly with coax. a TV transformer will probably handle a few watts but they are a bit lossy and I would avoid them whenever possible.

It's easy to make a dipole with wire as others have mentioned and you can tape the wires to a wood stick, PVC pipe or just about anything non conductive. Hang it outdoors vertically and bring the coax out sideways for a few feet before dropping down to the radio.

Most hams don't use a 2m antenna any better than a simple dipole and their in the form of a Cushcraft Ringo or most other antennas in the 4ft or less catagory.
prcguy

ampulman, Fantastic Reply! YOU actually used one?



what about trying as a "inverted V" dipole using the "ears"?



I am looking for a 300 - 50 ohm converter now. I am hoping to make a good match that way.

Any information you want to send is welcome.

 

[W2NJS]

One thing not mentioned above is that you should probably orient the "ears" setup so that the elements are vertical rather than horizontal. Almost all antenna polarization on 2M is vertical and you'll suffer a noticeable loss of signal strength if you run the antenna in a horizontal position. Turn the thing on its side and position it on the edge of a table if it's located inside the house.

 

[kb2vxa]

When it comes to a 2M antenna on the cheap it doesn't get any better than a ground plane made from a flanged chassis mount SO-239 and 5 20" lengths of 1/16" diameter brazing rod. Outdoors it must be weatherproofed with silicone bathtub sealant but since you ask about rabbit ears (I hear you Elmer, don't do it!) it gets even simpler. Here you can use 12AWG bare, solid copper wire you can scrounge and you don't need weatherproofing. For details just use your noodle, be creative!

Forget the rabbit ears, Bugs will thank you for it.

 

[pjtnascar]

That is a cool little antenna! If you're into the copper pipe thing, do a search for the 2 meter hentenna. I saw this recently and I'm kicking around the idea of building one.

 

[AK4GA]

The "rabbit ear" dipole antenna will have a feed point impedance of around 200 ohms. This translates to a 4:1 SWR unless you use a balun. My suggestion would be the twinlead j-pole. Plus the J-pole is much easier to hang vertical.

 

[joseph2020]

Thanks to all for the great comments and ideas.

LtDoc,

Instead of using a balun to change impedances, and depending on how those 'ears' are made to start with, why not just change the feed line to 50 ohm coax?

That's what I plan on using the rg-58 for, the feedline, but don't I still need to match the impedance of the "ears" to the line? Also my radio is only a HT, so putting the "ears" on top would be extremely difficult :lol:...the article suggest using it vertically. Thanks for the safety warning, but I don't plan to be anywhere near that thing.

prcguy

If you make the elements 19 to 20" long each the feed point impedance will be around 50 to 75ohms and you would feed it directly with coax. a TV transformer will probably handle a few watts but they are a bit lossy and I would avoid them whenever possible.

That is excellent news as I would rather not use a TV Xformer. Can you tell me how you figured out the impedance to be 50 - 75 ohms for 20"?

W2NJS, yep, the article explains to use it vertically (you didn't read it, huh) :wink:

pjtnascar

That is a cool little antenna! If you're into the copper pipe thing, do a search for the 2 meter hentenna.

I took a look at that and I probably will build one of those next...this time I want something super cheap, super easy that will work well.

AK4GA

My suggestion would be the twinlead j-pole. Plus the J-pole is much easier to hang vertical.

I have the materials for that except for a ferrite bead that my buddy says he has in his junk box. I will probably build this first as I am having a hell of a time finding the "ears"...I have looked in every thrift store in town, nobody has one....people just laugh at me when I ask for one.

Thanks to all for your helpful replies. If anyone has any more ideas, keep 'em comin'.

 

[joseph2020]

If I put this thing inside a piece of PVC, capped the ends, and brought out the connections for the feedline through some holes could I use it outside? would the PVC interfere with the signal at all, I would think not, but I did see one Slim Jim design that specifiacally warned against doing that. thanks in advance

 

[nanZor]

prcguy is right - just feed it directly with coax - with the elements adjusted for the right length for 2m.

Unlike the picture in the link, don't run the coax straight down next to the lower element. Bring the coax out perpendicularly for a few feet.

Inside the pvc? It can be done, but they typically detune the antenna a little bit so you'd have to adjust the elements a bit shorter than what you'd use in free space. The other issue is that the pvc can also distort the reception pattern - it may or may not be an issue in your case. Either way, I wouldn't use a telescopic outdoors for a very long length of time, even inside pvc, due to moisture ingress.

Note - don't be tempted to use black pvc. Any dye makes the detuning and attenuation worse. However, black pvc would be my first choice if I was to wind a coiled rf-choke out of coax on it for this very reason.

 

[ampulman]

Post removed, since you're likely going other route.

 

[LtDoc]

In PVC or out of it, all antennas have to be tuned for their particular use. That tuning may be a bit different if it's inside PVC, but there's nothing preventing you from doing that, is there?
- 'Doc

 

[RadioDaze]

If we can use rabbit ears for 2M, could we use, say, hamster ears for 23cm?

 

[W2NJS]

Deleted. Not worth writing about.

 

[joseph2020]

RadioDaze

If we can use rabbit ears for 2M, could we use, say, hamster ears for 23cm?

I suppose that would make a very portable antenna, huh? Pocket sized even! Thanks for the comic relief.

 

[joseph2020]

last questions on rabbit ears

I finally found the rabbit ears, I built the antenna by the plan, and it works good. It is also very portable. There was a 75 ohm connector, 300 ohm twin lead feedline, I took that off.

I attached a RG-58 cable for the feedline, with a BNC on the other end for the radio. I stretched the "ears"to form a straight line and hung it vertically. It would probably work better with a closer impedance match (currently 75 to 50 ohm )

2 last questions:

1) I can adjust this antenna anywhere from 1/2 wave to 1 wave for 146 Mhz by shortening or lengthening the elements .
is full wave better for a small antenna like that?

2) On the antenna elements I can choose what thickness rabbit ear to choose from 1/8 to 1/32 inch or less to make the right length.
I would think the thicker elements are better? Does this matter enough to make a big difference in rx or tx at 2 meter?

The antenna works as is, I am trying to squeeze every bit of performance out of it I possibly can. Any help is appreciated.