Piggie

Combining a UHF and VHF antenna w & w/o amps

To combine them without amps is pretty simple.
If on a common mast most often the UHF antenna is the higher one or on top, but not always. If the VHF station is much farther away like my case, my VHF is on top. But in general the UHF is smaller and lighter and mechanically if no other issues is more stable mount above the VHF. A minimum separation should be at least 4 feet.

Note: Any of the diagrams below where the UVSJ is between the power supply and the amp need to be power passive on the VHF side. Not all models are, so buy the ones from Hollands or Pico Macom which at this time are both power passive on VHF.

Note: The CC7870 is power passive on only one side. So if you use it between the amp and power supply be sure it's through the passive side. Some other combiners are passive on both ports, some on only one port, and others on neither port. If you are not sure and own an ohm meter or continuity light they can be tested for a DC connection.

Combing separate UHF and VHF no amp

UHF Antenna
|
UVSJ -------> TV
|
VHF Antenna

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Combining a UHF and VHF with an amp

If you want to add a mutual amp simply put one after the UVSJ

UHF Antenna
|
UVSJ -->Mast Amp-------Power Supply Inside--> TV
|
VHF Antenna

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What if your UHF is very strong and will over load the amp? But the VHF needs help?

Combining a UHF and VHF with only the VHF side amplified

UHF Antenna
|
UVSJ -------------Power Supply Inside--> TV
|
Mast Amp
|
VHF Antenna

Note this only works on the VHF side with a UVSJ. I won't work on the UHF side.

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But if the UHF side needs help? This gets a little more complicated of an answer, but there are really just two ways to do this.

Combining a UHF and VHF with only the UHF side amplified

1) This way involves using a combiner splitter. Now remember they have 3.5 db loss for each antenna (as opposed to UVSJ at 0.5 db), so the VHF side has to be good and strong to use this configuration, as you loose half it's reception! The UHF doesn't care because the amp is ahead of the combiner over coming it's loss.

UHF Antenna
|
Mast Amp
|
CC7870-------------Power Supply Inside--> TV
|
VHF Antenna

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2) This involves using 3 UVSJs in a cascade

UHF Antenna
|
UVSJ1 --UVSJ2_UHF--UHF Amp----Power Supply Inside-UHF_UVSJ3--> TV
|
VHF Antenna

This forum won't let me draw it but there is also a jumper between the VHF ports of UVSJ2 and UVSJ3 not shown.

The idea here there is less loss on the VHF side (1.5db compared to 3.5 with a combiner)

To write it out:
1) Antenna coax goes to USSJ1 where they are combined to one coax.
2) That coax goes to UVSJ2 common port (UVJS1 and UVSJ2 common ports are connected with one coax).
3) From UVSJ2 VHF side a coax is run indoors
4) From UVSJ2 UHF side a coax goes to the amp on the mast.
5) Output of the Mast Amp coax goes inside along with the VHF coax.
6) Inside the house, the UHF Coax goes to the power supply for the amp.
7) Inside the house the VHF coax goes to the VHF of UVSJ3
8) Inside the house the output of the power supply goes to UHF of UVSJ3
9) Common port of UVSJ3 goes to the TV

Note there are two coaxes going inside.

This is nearly a cluster bomb of UVSJ's but in fact there is 2db less penalty than using a simple splitter. The UHF side does have 1 db loss before the amp, but that should be acceptable.

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Combo antennas can be amplified on one side also (either VHF or UHF) with a UVSJ.

Amplifying the VHF side only of a Combo Antenna


Combo Ant--Com_UVSJ1_VHF--Mast Amp--VHF_UVSJ2_Com--Power--TV

Here I can't show on the digram the jumper from UVSJ1_UHF to UHF_UVSJ2

To write it out:
1) Antenna to Common on UVSJ1
2) Cable from UHF of UVSJ1 to UHF UVSJ2
3) Amp between the VHF ports of UVSJ1 and UVSJ2
4) Cable from Common of UVSJ2 to indoor Power Supply
5) Output of the indoor Power Suppy to TV.

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Amplifying the UHF side of a Combo Antenna

This is just like the example above of only amplifying the UHF side of separate antennas with UVSJ.

It's the same sequence you just don't need the first USVJ because the antenna is already combined UHF/VHF.

UHF Antenna
|
UVSJ1_UHF--UHF Amp----Power Supply Inside-UHF_UVSJ2--> TV
|
VHF Antenna

This forum won't let me draw it but there is also a jumper between the VHF ports of UVSJ1 and UVSJ2 not shown.

The idea here there is less loss on the VHF side (1.0db compared to 3.5 with a combiner). While the UHF only has 0.5 db before the amp.

To write it out:
1) Antenna coax goes to USSJ1 common port.
2) From UVSJ1 VHF side a coax is run indoors
3) From UVSJ1 UHF side a coax goes to the amp on the mast.
4) Output of the Mast Amp coax goes inside along with the VHF coax.
5) Inside the house, the UHF Coax goes to the power supply for the amp.
6) Inside the house the VHF coax goes to the VHF of UVSJ2
7) Inside the house the output of the power supply goes to UHF of UVSJ3
8) Common port of UVSJ2 goes to the TV

Note there are two coaxes going inside.

EscapeVelocity

Very informative. Thanks!

EscapeVelocity

This is a fantastic post, and doesnt deserve to pass without comment.

Thanks Piggie.

Piggie

Thanks for the thanks, I am passionate about antennas. Most of my knowledge is seat of the pants. I should get some antenna modeling software and go the next level but guess I am old school too, when you read the ARRL antenna manuals and went out in the back yard and tried to build one.

Again, it's great to see you over here on this forum. It's a very friendly place.

fessyjout

Is this what you mean piggie?

amp setup

EscapeVelocity

Hello fessy, I dont know where Piggie is, but I think the power is run through the coax cable intself via a power injector, which shoots a low voltage DC current up the line. You will need to make sure that the UVSJ you get, passes DC current on its VHF port.

This is so you only have to run one cable to the atnenna location on the roof or tower or where-ever it may be.

Welcome to the forum. Im sure Piggie will be around soon.

Piggie

I need to update the post. Turns out not all UVSJs or HLSJs are power passive on their lower frequency side. But the Hollands and the Pico Macom are both power passive on the low side. Also turns out they are about the best ones you can buy, at least for the money.

So compared to your or who ever's drawing EV pointed out the difference. With the proper UVSJ you don't need a separate wire to feed the amp if it's only on the VHF side. The power will go up the coax, be it DC or low voltage 60Hz AC.

But note, this will not work the other way. The UHF side is blocked for all frequencies including DC for all frequencies below 470 MHz. I know of no UVSJ that is power passive on the UHF side due to the way they are built.

DaGrinder

I have access to Pico Macom locally, but from what you're saying, it should be fine to use? What's the difference if they are power passive or not?

Piggie

From everything I have read the Pico Macom and the Hollands are identical. Might even be made in the same place and private labeled.

Yes, the Pico Macom is very good.

SweetPetes_66

Ok guys, I was just reading thru this thread, because I was just about to order a UHF antenna to stack on top of my combo UHF/VHF that is working good for us at least, on the VHF side, not so good on the UHF side. I don't have any equipment to measure signals except my converter boxes, the VHF channels are coming in at 50-60% on the RCA box we have, the UHF signals are all around 10-14% at best. I was going for the 91XG UHF antenna, with a CM 7777 pre-amp, with the antennas mounted at least 4ft. apart. After reading this info do you think I'll have issues, as in the VHF being too strong, that I'll have to separate the signals oor however you say that right. I live in a severe fringe, and have run you guys thru my TV fool info a couple months ago, I just got some time to deal with now, and as I said going to order the stuff today, unless I hear something bad about this set-up. Thanks again, as always