Unknown Yagi Antenna

I was recently given a yagi antenna that belonged to another ham operator years ago. It is a 14-element beam that is fed from the middle and has a scissor pattern near the back across several elements. The reflector is about 14 inches long, the elements toward the middle are about 10 inches, and the director is about 9 inches, with the boom being 60 inches long. There are no markings about brand or model remaining on it. I'm trying to determine what ham band it is designed for based on the measurements. Is there any way to calculate that?

sounds like a KLM antenna. Very wide banded, Probably a 440 antenna.. . Really you have a 7 or 8 element. The drivers are sizzered together. Probably 5 elements that are tied together. They are the drivers.If you are low in the 440 band, electrically you go to the longest sizzeded element. You rf goes to the point of least resistance. KLM antennas were pricey .If you have a swr meter, feed it with 5 watts, and read it. 5 watts will not hurt a thing.

A picture might help... you're sure it's not a UHF TV antenna? Length seems to be around 440 MHz.

For a 1/2 wave antenna, use the formula of 468 divided by the frequency in megahertz = the length.
It's 1.06, or about 12 inches.

Gilligan said:

I was recently given a yagi antenna that belonged to another ham operator years ago. It is a 14-element beam that is fed from the middle and has a scissor pattern near the back across several elements. The reflector is about 14 inches long, the elements toward the middle are about 10 inches, and the director is about 9 inches, with the boom being 60 inches long. There are no markings about brand or model remaining on it. I'm trying to determine what ham band it is designed for based on the measurements. Is there any way to calculate that?

Click to expand...

This sound like the antenna is a mix between a log-periodic and a yagi.

The elements that are crossed are considered log-periodic and together they are considered the feed. Log-periodic element groups are fed from the front, which in your case, is the middle of the antenna. Log-periodic element groups are used to increase the effective bandwidth of the antenna. Generally, in that group, the longest element determines the lowest operating frequency and the shortest element determines the highest operating frequency. The other elements in that group handle the frequencies in between the high and low.

At any particular frequency, only a few (3-4) of the elements in that group are active. As the frequency changes, from low limit to high limit, the active element group moves from the rear of the log-periodic group (longest elements) to the front of the log-periodic group. The other elements in that log-periodic group are inactive, because they are either too long or too short to be effective. The lengths of each element in the group are adjusted so that there is a smooth transition going from the low to high operating frequency.

The other elements, in front of log-periodic group, are directors they help enhance a specific section of the covered bandwidth. This may be a area where the log-periodic group has a bump at a specific frequency.

While log-periodic antennas have good bandwidth, they don't have very high gains. For example, a yagi for 440 MHz with a 60 inch boom will have about 11.5 dBd of gain. But in the case of your antenna, only half of the antenna contains directors lowering the possible gain by about 3-6 db. However, that is still a good gain figure.

To determine the actual operating frequency, you need to accurately measure the length and spacing of each element in the log-periodic element group. You also need to measure/calculate the apex angle that is formed by the elements. Then you could work the log-periodic calculations backwards and determine the operating range. Information on the log-periodic antenna is easily found on the net.

Martin - K7MEM

Yes it does sound like a KLM wide band Yagi with log periodic feed. I just got a new old stock small version with about 6 elements and the KLM coaxial balun. Mine is rated 440 to 520MHz but I think the longer versions had a little less BW. The only other company I've seen with a log periodic feed on a Yagi is the TACO antenna company.
prcguy

teufler said:

sounds like a KLM antenna. Very wide banded, Probably a 440 antenna.. . Really you have a 7 or 8 element. The drivers are sizzered together. Probably 5 elements that are tied together. They are the drivers.If you are low in the 440 band, electrically you go to the longest sizzeded element. You rf goes to the point of least resistance. KLM antennas were pricey .If you have a swr meter, feed it with 5 watts, and read it. 5 watts will not hurt a thing.

Click to expand...

prcguy said:

Yes it does sound like a KLM wide band Yagi with log periodic feed. I just got a new old stock small version with about 6 elements and the KLM coaxial balun. Mine is rated 440 to 520MHz but I think the longer versions had a little less BW. The only other company I've seen with a log periodic feed on a Yagi is the TACO antenna company.
prcguy

Click to expand...

Will second that on what prcguy said sounds like a KLM log periodic antenna......

Sorry for the delay... I'm attaching a few pictures of that beam antenna in case it would help to identify which bands it may operate on.

I also have an unidentified whip antenna that is likely for HF. The larger base part is 26 inches long and the stinger is 32.5 inches long for a total length of 58.5 inches. No idea but I'm attaching pictures of it also.

I just ordered an FT-817ND for Christmas so I'm excited about being able to finally use these antennas in a few days

That is definitely an old KLM broad band UHF Yagi with log periodic feed and balun. I have a 6 element version and its rated 440 to 512MHz continuous that I thought about putting on the RR classifieds.

There is not much info available on these antennas but I have the original instruction sheet for mine.
prcguy

Gilligan said:

Sorry for the delay... I'm attaching a few pictures of that beam antenna in case it would help to identify which bands it may operate on.

Click to expand...

The yagi is a KLM and was built for 440-450 Mhz ham band many years ago. Maybe
about 1970. They were very good antennas and were for mounting vertical. That's
why it has the U-Bolt holes are at the rear of the boom..There is also a 16 element
version but was made to mount horizontal for 432 SSB/CW operation.

The whip antenna was very interesting to see. I own one exactly like it and was
never able to determine who built them. The antenna is for 140-170 Mhz and
it is adjusted by sliding the lower tubing in-out to adjust the antenna for the portion
of the band needed. I used mine on 2 meters for a portable antenna for years.
For a compact antenna it works well and worth cleaning up and keeping..

W3DMV said:

The yagi is a KLM and was built for 440-450 Mhz ham band many years ago. Maybe
about 1970. They were very good antennas and were for mounting vertical. That's
why it has the U-Bolt holes are at the rear of the boom..There is also a 16 element
version but was made to mount horizontal for 432 SSB/CW operation.

Click to expand...

Awesome! Thank you both for your help!

Any chance I could use this one for 432 SSB/CW if I turned it horizontally?

Also how about using it for satellite ops?

Not 100% sure but it looks like this model would then be called the KLM-420-470-14.

I found some manuals online at parc.org.za in case any of you are interested. Also, there is a KLM yagi antenna advertisement (PDF) at http://www.worldwidedx.com/attachments/klm-antenna001-pdf.7490/