Baluns (Brands, Designs, Losses, DIY Loops, etc.)

[Xauto]

Sorry. I do not have anything to test the bandwidth.

[Josef W. Segur]

Having read this thread from beginning to end, I'm impressed by the amount of thought and effort many have contributed.

The balun using a half wave transmission line section to get the needed 180 degree phase shift is obviously very efficient if well constructed. There have been many looking for a balun which would work for both VHF Hi and UHF, but nobody has pointed out the happy coincidence that UHF band frequencies are almost exactly 3 times those for VHF Hi, and that 1.5 wavelengths also gives a 180 degree phase shift. So a balun designed for channel 10 (195 MHz.) ought to also work well on channel 33 (585 MHz.).

Unfortunately, for frequencies away from the design point the UHF response will drop off 3 times faster than a UHF-only version. So this idea would be most useful in locations where the available UHF channels are not widely spread, though might cover most of the current UHF band adequately.

[x4mer]

This would make a balun tuned for 7 (WBBZ), also tuned for 23 (ION). Two of the weakest stations locally, peaked with one balun.

[Archerotor]

I realize that Baluns can have ranges of dB signal loss. I wanted to know if anyone has recommendations as to Channel Master or Steren. My AntennaCraft VU-160XR VHF/FM/UHF looks to have a Steren (Item # 200-490) as original equipment- it has the 300 Ohm twin-wire leads with the spade connectors crimped on.

Solid wire hook terminals vs. spade connectors?
The Steren 200-495 has the wire hook connectors, like the Channel Master CM 94444.

[oneolddude]

After reading this thread I need some clarification.

Is it fair to conclude that commonly available off the shelf baluns for OTA use that are randomly selected (not hand selected after measurement) typically have signal loss of about 2 dB or more in the FM and HI VHF bands and 4 dB or more in the UHF band?

If that is not a fair conclusion, what can one expect from randomly selected commonly available 4:1 baluns for OTA use in the FM, HI VHF and UHF bands respectively?

Thanks

[ProjectSHO89]

Is it fair to conclude that commonly available off the shelf baluns for OTA use that are randomly selected (not hand selected after measurement) typically have signal loss of about 2 dB or more in the FM and HI VHF bands and 4 dB or more in the UHF band?

If you look at the plots that ADTech provided (posts 670 and immediately following), it looks like it's more like around 1 dB at VHF and up to 2 or 3 dB at the higher UHF frequencies per balun.

[bentoronto]

What we are all really crying for is a feasible home-brew method of measuring balun or quarter-wave performance (or antennas, etc). Or even just good ground rules for doing better shade-tree* testing.

How can a person with a modest collection of test gear, old tuners, rental/borrow/temporary access, ability to bread-board stuff, or even a willingness to buy some cheap DIY kits, make even just relative comparisons between devices.

(Having spent a lot of time eyeballing so called "signal strength" displays, I know that is a poor approach given weather and other imponderable variables and the crudeness of these displays (just three bars on my Sony FM-HD tuner). Any methodology to lever-up the goodness of these displays so as to make them useful?)

PLEASE.

Ben
*auto mechanic term for fixin' your own car or motorcycle under a shade-tree

[ProjectSHO89]

An "entry level" spectrum analyzer with tracking generator is $1500 from Rigol, for example. Otherwise, you'd need a programmable RF signal generator (ebay, several hundred bucks) plus an RF power meter plus time and patience.

A lot depends on the level of accuracy you want. Since the tendency around here is to split hairs (or fractions of a dB), you'd need something fairly accurate. Accuracy isn't cheap.

[bentoronto]

Originally Posted by ProjectSHO89

An "entry level" spectrum analyzer with tracking generator is $1500 from Rigol, for example. Otherwise, you'd need a programmable RF signal generator (ebay, several hundred bucks) plus an RF power meter plus time and patience.

A lot depends on the level of accuracy you want. Since the tendency around here is to split hairs (or fractions of a dB), you'd need something fairly accurate. Accuracy isn't cheap.

Many thanks for information. While you are right about some hair splitting, I was hoping for a clever test strategy or single-frequency test or something (rather than cash) to get even just a little leg-up comparing two components.

Ben

[holl_ands]

Back in 2008, I posted a Test of Insertion Loss for numerous Baluns:
http://www.*************/t/381623/th...#post_13581150
[Oh, drat...overwrote the OTHER forum name which shall remain nameless.]
Balun Test Results also found here: http://imageevent.com/holl_ands/files/ota

At the time, I used what (little) I had at hand: A Cable Box which generates
signals on nearly all OTA UHF channels and a few in VHF Band.
I used built-in (dBmV) signal level displays in the Cable Box's Diagnostic Menu.
[Perhaps you would need to find a willing neighbor who has Cable.....]

LINGO: Look for FDC and QAM256 signal levels. RDC is Reverse Data Channel
BACK TO HEADEND. It helps to cycle through all DISPLAYED CABLE "channel"
numbers and enter FIRST ONE next to a list of ACTUAL EIA frequencies so you
have an ORDERED list and can pick a handful of "channels" for desired test freqs.
Recall that there can be MANY different Cable "channels" on each QAM256.
Note that OTA Broadcast frequencies are NOT all the same as Cable EIA freqs:
http://www.jneuhaus.com/fccindex/cablech.html

On my Time Warner Cable Box, to access Diagnostic Menu, hold down SELECT
key on R/C until you see the MAIL Icon appear on front of Cable Box. Then
press the DOWN-ARROW key on R/C. Use PG-UP and PG-DN to cycle menus
and EXIT to exit. [Other systems may require some research....]

Measuring pairs of identical back-to-back Baluns and then dividing by two,
I determined the insertion loss for an individual Balun. [ASS-U-ME equal]
I did this for several identical pairs of Baluns, picking the BEST of the bunch.

Knowing the insertion loss vs frequency for THAT Balun, I could then measure
the back-to-back insertion loss for a non-matching Balun and subtract away
the loss in the "measurement standard" Balun.

Since Cable Box provided measurement to nearest 1 dB, which I then divided
by two, I believe the accuracy is ABOUT +/- 0.5 dB, although may be slightly
worse if signal level jumps around one digit.

Today I would use my Digiair Pro Signal Level Meter, with 0.1 dB resolution,
but fluctuation in Cable Box Signal Levels may still limit accuracy to +/- 0.5 dB:
https://www.perfect-10.tv/PDFs/Equip...20Pro%2005.pdf
http://www.sadoun.com/Sat/Products/Perfect/digiair.pdf

About $200, the newer Digiair Pro 2 is much more sensitive than original
Digiair Pro, which requires a Preamp for sensitive signal measurements.

Unfortunately, the usual sources indicate that they have been discontinued,
so maybe there is a new model on the way???? Check EBay for used items.

[bentoronto]

Ahhhhhh, there's a great idea for a testing strategy inside holl_ands post. To overcome the unpredictable variation in signal level when doing measurements, a person could use a Cable feed.

Is it correct to say that the Cable companies keep their signal level pretty constant?

Now.... at the other end, we need something to measure signal strength. I am not at all clear what the display on a TV means. I suppose I might understand it better if I had any idea who point in the TV's circuit drove the display.

Also, say a display had 10 "bars". Are these more or less linear with signal strength or are they a power function whereby the lower bars are more sensitive?

Ben

[holl_ands]

Cable signal levels have some statistical fluctuation (just like OTA ATSC) and
vary by up to several dB from one QAM carrier to another....so you have to
measure each carrier before and after insert Balun and should then go back
and verify that signal level without Balun didn't change...and use the difference.

Unless there is a specific signal level in dBm, forget trying to use a "Signal Quality" display.

Some CECBs have been calibrated against a Signal Level Meter, see rabbit73's
post #10325 on 3/31/09 in the Antenna thread:
http://www.*************/t/381623/th...#post_16166929
[You know...in that other forum that shall remain nameless.....]

BTW: There is a Signal Level Meter thread on this forum.

[roger1818]

Originally Posted by ProjectSHO89

Otherwise, you'd need a programmable RF signal generator (ebay, several hundred bucks) plus an RF power meter plus time and patience.

Rather than use a RF signal generator, a better option would be to use a tunable RF modulator (You should be able to pick one up fairly cheaply online), that way you have a real signal you can tune to.

[rabbit73]

It is possible to switch baluns on an antenna to see which one is better for a particular channel, but OTA signals can vary in strength. The ultimate test, however, of a balun is how it performs with your particular antenna. I use the following setup to measure balun loss:



Be sure to use good quality A/B switches, the slide-type switches that are in a case like a splitter don't hold up very well.

When I use my analog signal level meter, it is possible to interpolate to the nearest 0.1 or 0.2 dB, especially at mid-scale where the 1 dB divisions are wider. When I use my digital signal level meter, it reads in tenths of a dB.

It is not necessary to spend a lot of money on a signal level meter if you are careful to buy a good used one. An old analog meter will work fine because you don't need absolute accuracy of the dBmV value, just good linearity of the dB scale which can be checked with the built-in attenuator. I got this meter for $50:



When I must have a steady signal, I use a Channel Plus CP5415 or a Blonder Tongue HAVM-1UA modulator as suggested by roger. If you connect the modulator to an antenna to radiate a test signal and receive that signal with your antenna under test, you can switch baluns without worrying about changing signal strength. The test signal must not be any stronger than necessary to avoid interference; it should be similar in strength to a tracking generator in a spectrum analyzer.