Here is my use for a UVSJ.

My antenna is used to pick up Toronto, Hamilton and Buffalo stations. I have a strong local VHF station (channel 13) that is on the opposite side of my apartment building. Picking up this station without multipath interference is difficult. I get lots of reflections.

The station is strong and local. I found an area in my apartment where multipath interference is minimal. I connected a small telescopic antenna to the VHF side to pick up the local station, my TO/Hamilton/Buffalo antenna to the UHF side. It combines to the two antenna and I can watch both local and distant tv stations now.

http://datalore.ca/sandbox/ZZ130803E5.jpg

Here is my dilema folks....I have a cm4228 ( uhf ) and also recently bought a cm 3020 long range vhf/uhf/fm antenna. I am told that there will be interference between the 2 antennas because of the uhf, and that I need some equipment to block the signal from one

Anyone know what the name of this thing is?

cheers

UHF/VHF Diplexer, commonly referred to as a UVSJ.

Connect the 4228 to the UHF port and the 3020 to the VHF port. See the post immediately above yours for a practical example.

Thanks for the reply. It will have been easy for me to search if I knew what I was looking for, which I didn't.

Now I know what to ask for at the store

@majortom: I've seen that kind of interference before. At first, I too believed it was electrical interference. After some troubleshooting, I discovered that it was very strong FM noise. If you can somehow attentuate FM, or use an UVSJ to attentuate VHF, you may discover that the noise will disappear or diminish. I also found the issue to be intermittent--furthering my initial suspicion that it was electrical in nature.

When you're in close proxmity to an FM transmitter, the interference harmonics will roll on up to your UHF stations as well (if your equipment allows it). And this issue is exacerbated if you use a broadband pre-amp that amplifies the FM band as well.

Jase88,
Remember this?
Regarding my post in here,
http://www.digitalhome.ca/forum/showthread.php?p=1099344&highlight=electrical+interference#post1099344

Do ya think it could also be static in the air?
i.e. - That tower down the rd from me is a guyed structure, casually passin by walkin the dog whatever, I've literally seen / heard arcing come down the guy wires on days/nights when the air is unstable. I don't see the sure sign of it everyday, but once in a while. And I have seen the symptom once in a while with the UVSJ in line, to filter out the VHF Band between antenna and Pre-Amp input.

Recall seeing the same thing quite a bit in my "HF Days",
i.e Large Wire antennas pickin up static while hangin in mid air
on days with thunderstorms in the area...discharging the static charge to ground,
etc...
Guess I'll have to pay more attention to the weather, when it does happen, take a stroll down there
sometime...Even listen for it on an AM radio or sumthin too. If I hear any crackle / Pops at the same time
the TV Signal Degrades, then on to sumthin. If not, then back to ur theory I guess.

Either way I can still steer away from it with the rotor.

m.t.

Electrical arcing generates RF noise--so it could definitely be that.

In another forum, I saw a post where someone was experiencing the same type of issue. The poster lives in a older neighbourhood with aerial hydro feeds. The problem immediately disappears during rain. And it would become erratic during windy conditions.

Now from my days at a local hydro utility (did IT work for them, not a linesman), I know that electrical arcing happens frequently in distribution lines. It's not always easily visible (especially during daylight), so hydro crews diagnose it by using infrared cameras to watch for hot spots.

If the above conditions apply to you (older aerial hydro infrastructure), you may want to note during the next rain if it goes away.

If we have any hydro professionals here, maybe they could offer their take on the issue...

These things can be tricky to diagnose...so it just comes down to trial and error and attempting to eliminate possibilities as you go along.

Thx Jase, naw definitely no power lines around here, at least nothing super high voltage, just ur normal suburban distribution u'd see in any residential
area. But like I said, I know I've seen them guy wires arcin before, at night
was visible, almost like fireflies crawlin down the guy wires...

Have seen it actually get struck by lightning, now that was cool...

Thx Jase, naw definitely no power lines around here, at least nothing super high voltage, just ur normal suburban distribution u'd see in any residential
area. But like I said, I know I've seen them guy wires arcin before, at night
was visible, almost like fireflies crawlin down the guy wires...

Have seen it actually get struck by lightning, now that was cool...
AM radio towers are famous for arcing. With AM, the tower itself is the live element, the guy wires have insulators in line. They can arc when wet.

AM radio towers are famous for arcing. With AM, the tower itself is the live element, the guy wires have insulators in line. They can arc when wet.

yup I know that, AM Towers are "Hot Towers".
And there is an AM Station right next to this FM station, but the FM station is the guyed, and the AM station is a self support.

The FM Station is the one I was referring to seeing arcin off the guy wires in the past...

BTW, I saw the sure sign of it again yesterday evening in the Analog Stations, was probably the worst I've ever seen it (Might have been the day before Evening (?), this week's been a blur..). Weather was dry and rather Windy though at the time for sure, some Rain / Thunderstorms had passed earlier in the AM that day if I recall.

Edit: TomF1, I'm eating crow, stand corrected. Just scoped it out again, walkin the dog, and I did have it backwards. The guyed tower
is indeed a "HOT" AM Station, can see the feed at the base of the tower, but it also has what look like FM Dipole stacks at the top, 6 of 'em. There is still the lower Self Support next to it, with similar but not identical dipole stacks at the top. So, the arcing theory
off the guys making more sense now... Not much I can do about that I'm thinkin, but steer the antenna in to a null there
when it's happening...What I been doing.

I recently picked up an older Armaco AL2551 analog "standing wave bridge & field strength indicator" from a street sale. It has what looks like 1/2" connectors.

Can this be used in setting up OTA gear?

A picture of it is here:

http://i525.photobucket.com/albums/cc337/my_pics48/IMG_0006-1.jpg

No.

The impedance is 50 ohms on these boxes while TV coax is 75 ohms.

You would also need a transmitter of some sorts for this box to function. The way it works is it measures the difference between the signal going to the antenna and the signal that is reflected back from the antenna.


These boxes are typically used for setting up HAM radio antennas.

Thanks. I have just the guy in mind that I will give this to.
OTA set up -- for me, back to trial and error ;)

Those are PL259 connectors, which makes it most likely that it was intended for CB or amature radio.

Can't think of any way to use it for OTA.

When using a cable splitter as a combiner (modding 4228HD ant), can satellite splitters be used the same as CATV splitters?

The ones I have in my shop are '5-2500 MHz' splitters. The printing on the device says they are "Power Pass". Methinks think they came from the Dollar Store or such.

These should work with OTA. There is little difference between many 75 ohm splitters sold for satellite and OTA use. Just be aware that power blocking satellite splitters will block the power to a mast mounted preamp on one leg. OTOH, they can be used to advantage to prevent back feeding preamp power to an OTA receiver.

If these "one leg pass" splitters such as the popular Perfect Vision PV22-233 only allow voltage on one side, does that affect the 4228HD dual balun/combiner mod when using a mast mount amp?

PolyMeR, if the splitter is below the preamp then yes, you'll need to make sure the preamp is on the DC Power Pass side so that it is receiving operating power. If the splitter is above the preamp (nearer the antenna) then it does not matter because the preamp is the terminus of that power circuit, not the antenna.

im trying block out as much as i can below UHF, will putting 2 UVSjs in series with antenna thru UHF legs cut down VHF and FM more than just one UVSJ?

Yes, it will attenuate the lower frequencies twice as much, assuming that the devices are equal.

Cap unused ports with terminators.

Isn't it the Combined/Line leg you need to connect to the antenna and the UHF leg to your TV ? In this case, it would go Antenna to Combined leg of UVSJ no1, UHF leg of UVSJ no1 to Combined leg of UVSJ no2, UHF leg of UVSJ no 2 to TV.