TV Fool - new help to identify UHF Yagi

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new help to identify UHF Yagi

Greetings.

I recently found this old antenna lying in my attic unused. Correct me if I'm wrong, but I believe it to be a directional UHF Yagi. I would guess it to be around 20-25 years old. The boom measures 70.5" It has 14 directors, 1 reflector, and I'm assuming the longer one on back is the driven element?

I'm trying to figure out who might have made it, what kind of gain it is capable of, and it's frequency range. I'm assuming it could probably achieve 15-16dbi? Wishful thinking?

http://imageshack.us/a/img21/6797/xzzm.jpg

I'm currently using this as my OTA antenna. I removed the old 300 ohm wire pair, and screwed on a 300 to 75 ohm balun. It's currently installed in an attic (temporary), and it does okay considering it's horrible placement. I have plans to mount this on an old Directv J-pole with a mast extender to get it outside and above the roofline.

Given the age of the antenna, it's possible that it's engineered for the older UHF band (CH-14 to CH-83). Still, it looks like it's in great condition. I don't know the make or model number, but a 14 director Yagi should give you the gain you've estimated.

Here is the output from "VK5DJ's YAGI CALCULATOR"

Code:

VK5DJ's YAGI CALCULATOR



Yagi design frequency =600.00 MHz

Wavelength =500 mm

Parasitic elements contacting a square section metal boom 25.00 mm across.

Folded dipole mounted same as directors and reflector

Director/reflector diam =6 mm

Radiator diam =6 mm



ELEMENT LENGTHS AND SPACING

The abbreviation "IT" means "Insert To", it is the construction distance from the element tip to the edge of the boom for through boom mounting



Reflector

262 mm long at boom position = 30 mm  (IT = 118.5 mm)



Radiator

Single dipole 232 mm tip to tip at boom posn =130 mm         (IT = 103.5 mm)

Folded dipole 257 mm tip to tip at boom posn =130 mm         (IT = 116.0 mm)



Dir        Length        Spaced        Boom position        IT        Gain        Gain

(no.)        (mm)        (mm)        (mm)                (mm)        (dBd)        (dBi)

1        230        37        167                102.5        5.4        7.6

2        227        90        257                101.0        6.9        9.1

3        225        107        365                100.0        8.1        10.2

4        222        125        490                98.5        9.1        11.2

5        220        140        630                97.5        9.9        12.1

6        218        150        779                96.5        10.7        12.8

7        216        157        937                95.5        11.3        13.4

8        214        165        1102                94.5        11.8        14.0

9        213        172        1274                94.0        12.3        14.5

10        211        180        1454                93.0        12.8        14.9

11        210        187        1641                92.5        13.2        15.3

12        209        192        1834                92.0        13.6        15.7

13        207        195        2029                91.0        13.9        16.1

14        206        197        2226                90.5        14.2        16.4



Spacings measured centre to centre from previous element

Tolerance for element lengths is +/- 1 mm



Boom position is the mounting point for each element as measured

from the rear of the boom and includes the 30 mm overhang.The total boom length is 2256 mm including two overhangs



The beam's estimated 3dB beamwidth is 31 deg



A half wave 4:1 balun uses 0.75 velocity factor RG-6 (foam PE)  and is 187 mm long plus leads



Here are some construction details for a folded dipole



Measurements are taken from the inside of bends

Folded dipole length measured tip to tip = 257mm

Total rod length =543mm

Centre of rod=272mm

Distance HI=GF=106mm

Distance HA=GE=133mm

Distance HB=GD=161mm

Distance HC=GC=272mm

Gap at HG=10mm

Bend diameter BI=DF=35mm



If the dipole is considered as a flat plane (see ARRL Antenna Handbook) then its resonant frequency is less than the flat plane algorithm's range of 10:1

GUM,
Thank you for the reply and information.

I also had the assumption that this antenna was used on the older UHF band. I say this because I believe it was used in conjunction with a VHF antenna, which I also dug out of my attic. There is also evidence left behind that they split the VHF and UHF signal into one with a splitter that I found.

If it was in fact designed to pick up 14-83, then it makes sense that it picks up all my local channels with the antenna pointed at roughly 300*
http://www.tvfool.com/?option=com_wr...46ae3318cc8876

Couple of other interesting tidbits....

Even though it appears that this was strictly designed for UHF, it picks up KFME (VHF-Hi) with ease.

Also, I was pleasantly surprised to see that it picks up KVRR very well off the back end of the antenna.

I believe this thing has some great potential for my purposes. Even though the attic placement is horrible, it still manages to pick up everything in green on the analysis report. I am having periodic issues with KXJB-DT & KVLY-DT pixelating and sometimes dropping momentarily (SNR will drop below 16), but I blame the placement for that. I can't wait to see what this thing will do on a 5ft mast mounted on my old dish j-pole!