It shouldn't. Just remember with the CM 7777 that you need to switch it to dual input mode instead of combined mode...

As a follow-up to http://www.digitalhome.ca/forum/showpost.php?p=1317493&postcount=857 I went about today trying to find a way to achieve reception of WADL, CHWI-26, and CIII-32. After going to Electrozad, Crescent Television Service and Turners and speaking with the respective staff who actually have knowledge about OTA, I decided that it was best to start by going to The Source at Devonshire and picking up a few different antennas. Now I did clear this with the store manager and he had no problem with me testing different units and returning them when I was done. I also had one of the sales reps tell me that it dependent on the size of my television screen for what antenna would work best. Sigh. Anyways, when I was at Turners I also picked up a piece of flat RG6 so that I could run the signal coming from the CM4228 through the door instead of the rig I had fed through the air conditioner slot (as per request of my landlord).

It is also worth noting that when I got home, I noticed that CIII-32 appeared to be coming in off the back-end of my CM4228 at about 45 points on my Access terminal. However my Samsungs were not getting a lock.

Now, my first intention was to go with one of the non-amplified antennas and mounting it outside, then merging the signal before the flat cable. While I was able to get CHWI-26 to come in, I couldn't find a sweet spot that was in an area that I could mount the antenna for WADL. After rethinking the situation, I setup the ganging to occur right at the input of the Samsung LN-T3242H. I found that all of the Terk, RCA and Nextec antennas except for the Terk FDTV1A was knocking out CBET. Luckily, I had an old Radioshack Attenuator kicking around. It has a dial with one side labeled MIN and the other labeled MAX. Once I put it in the line of the Terk before the merge, I was able to find a spot about a quarter of the way off of the MIN selection that got CBET, WADL, CHWI-26 and CIII-32. I also checked to make sure WDIV stayed solid and it did. The only downside was on WXYZ. But after unhooking the ganged setup, I attribute it to the flat RG 6 I installed. The signal now caps at about 75 and goes down to 55, mostly sitting in the 65 range.

I then moved the merge directly to my 4 way distribution amp so it would feed all 3 tuners. I was only monitoring the Samsung LN-T3242H at this point and I noticed CBET jumped from 2-3 bars up to 4-5 bars, and CHWI-26 went up to 5 bars. WADL is at 2-3 bars.

It's been about 4 hours now and so far I haven't seen any dropouts, except for a quick second of pixilation but there is lightning outside right now so I am attributing it to brief atmospheric interruption.

My question right now is, Electrozad for $30 plus tax had the Winegard CC-7870 antenna combiner. Does anyone think its worth getting? Right now my -3dB splitter seems to be doing a good job at combining the two antenna signals. They have no return policy...

It shouldn't. Just remember with the CM 7777 that you need to switch it to dual input mode instead of combined mode...
What he said....UHF performance is unaffected by attaching a Hi-VHF antenna to CM7777.
And if UVSJ is used to combine Hi-VHF AFTER the Preamp, the 0.5-1.0 dB UHF loss in combiner
is REDUCED by the Gain of the Preamp to a very tiny fraction of a dB.
PS: Since it is a FULL-BAND device, Winegard CC-7870 will have a higher 3.5 dB insertion loss.

Only concern I have is whether amplifying Hi-VHF signals and also FM signals would cause "overload"
problems (2nd Harmonics are in Hi-VHF band), which could prevent reception of weak Hi-VHF stations.
I think the FM Band Trap in the CM7777 is a narrow band notch type, which only works against a
narrow range of FM stations. The Cascade Preamp+Distribution Amplifier could also be a problem
if the signal levels going into the Tuners are too high....

For this reason, you should also try combining UNAMPLIFIED Hi-VHF signals AFTER the Preamp,
using a UHF/Hi-VHF Combiner with DC PASS-THRU on the UHF port, such as R-S 15-2586
or Antennas Direct EU385CF (NOT Pico-Macom or Holland UVSJ which are DC PASS on Hi-VHF port).

With Solar, Galactic & Man-Made Noise levels being fairly high in the Hi-VHF Band (and much
higher in Lo-VHF), Preamps frequently won't help VHF signals in urban areas anyway, esp.
if you're using a Distribution Amplifier to solve the multiple drop problem....

Could you post your TVFool and FMFool results...preferably new runs to get latest updates....

Not sure if you were talking to Brightonian or me, but if it were me here is my TV Fool...

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d83878fa3ea1149

My guess is that stacking/ganging antenna in the age of digital signals (and with new tunners that handle multipath) should be a little easier then it was in the analog period.

It will be harder. See Post #16 in the OTA FAQ for how analogue signals aid aiming in these types of configurations.

I don't mean aiming. Since ghosting due to multipath doesn't happen with digital signals, and modern tuners are better to handle multipath without dropping the signal entirely, I suspect it may be easier.

I combined totally dissimilar antennas (different directions), one amplified, one not, and the only obvious loss was to my single remaining analog station.

Change your mind at all?

My guess is that stacking/ganging antenna in the age of digital signals (and with new tunners that handle multipath) should be a little easier then it was in the analog period.


It's absolutely harder. With analog, you could see the defect right on the screen and have instant feedback as to what effect any changes you'd made did to your reception. With digital, it pretty much either works or it doesn't.

It's a real crap shoot. Roll the dice, sometimes you get lucky, most of the time you loose.

OK - let me narrow the scope. For those w/ reasonably strong signals, but coming from two different directions (stacking).

My point is that a bit of a interference is instantly visible w/ analog. With digital - a slight loss and you still get the picture all the time.

I mean no disrespect to the more technical members - just a spirited discussion.

Not sure if you were talking to Brightonian or me, but if it were me here is my TV Fool...

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d83878fa3ea1149

When a Distribution Amplifier is used with a Preamp, it is likely that one or more
components is "Overloaded", which means Third Order Intermod Noise blocks
reception of weak stations. CM7777 is probably overloaded and if not, the high
Gain of the Preamp is probably overloading the Dist. Amp. Even w/o a Dist.Amp.
in high signal level areas it is also possible to overload the DTV's Tuner.
Worst Case---you're looking at a Triple Whammy.....High Gain Preamps are for
RURAL, low signal level areas....

I provided a "DTV Preamp Overload Calculator" and "Third Order Intermod Calculator"
to help assess the severity of the problem and also determine the allowable Gain of
the "optimum" Preamp....which MAXIMIZES SFDR (Spurious Free Dynamic Range):
http://imageevent.com/holl_ands/files/ota [Search forum for more info re "SFDR".]
"DTV Preamp Signal Overload Calculator - Rev L" update simplifies VHF calculations.

Spread sheet can do a Gain-Loss Budget on your strongest VHF & UHF station(s) to
ensure that input signal levels to both your Preamp and Distribution Amplifier are not
too high. To use spread sheet, pretend Dist. Amp. is the Tuner. The input to the Tuner
(i.e. Dist. Amp) should not exceed -15 to -10 dBm (a guesstimate, -15 dBm is better).

Once you know Sih (HDTV DTV Input..i.e. Dist Amp Input) signal level, add the Gain
of the Dist. Amp. and subtract Loss through various RF Splitters and Coax going
to your DTV's. This level also should not exceed -15 to -10 dBm (a guesstimate).

If the CM7777 is overloaded, there is nothing you can do after the Preamp to help.
The choice of Preamp Gain and Noise Figure must be matched to the expected set
of strong signal levels. A good Lower Gain alternative would be either W-G AP-4700
(19 dB UHF Gain & BYPASS on VHF) or W-G AP-2870 (19 dB UHF, 17 dB VHF).
Spread Sheet results might also indicate whether you need an even lower Gain
Preamp, such as W-G HDP-269 (12 dB UHF/VHF).

A SMALL amount of loss can be placed in front of the Preamp...or Dist. Amp. to
reduce Intermod Noise (and also increases Noise Figure). There is 3 dB of
Intermod Noise reduction for every 1 dB of Loss...hence inserting 4 dB Loss
RF Splitter reduces Intermod Noise by 12 dB. Reducing the signal level going
into the Dist. Amp. is something easy to do that might yield a significant benefit.

Due to the loss in RF Splitters in the Dist. Amp. (et al.) and Coax Loss, it is not
easy to overload a multiple DTV Tuner configuration. But be sure to do the
signal level calculation and perhaps insert a SMALL amount of additional Loss
if any are within or close to the Overload threshold.

If I stacked 2 y10 7-13’s and added a DB8 on a single mast with a rotor connected to 7777 what spacing/order could I use that will not exceed the mast length/wind load above the rotor and maximise reception of 7 & 11?

Thanks for your response.
Will adding a VHF HI antenna to my CM4228HD have any negative impact on my UHF performance?
I want to chime in on this. ION from Batavia was fussy, DB8 needed to look right at it or no lock. I added a suburban VHF antenna to my DB8 using 7777 dual inputs, formerly set to combined and got a surprise. After the VHF was added I could point toward Toronto (80 degrees or so more west) and I can not kill it. So it may be a plus to do this.

Hi, My friend in Aurora bought a second DB8, combiner, and two equal pieces of cable. We stacked the DB8's (pointing in the same direction) and put one on top of the other on the same mast on top of a roof on a tripod. When both antenna's are hooked up we lose all Buffalo stations, but Toronto's come in fine. With just one antenna (either), the buffalo's and Toronto come in. The reason for doing this was to increase the signals, but looks like it might not work. Any ideas what we did wrong?

Yeah, the antennas were the wrong distance apart (too close?). I'm not sure what the general consensus is on vertical separation for DB8 stacking, maybe somebody can confirm?

There are two other ways for increasing signal strength other than combining/stacking.

1) Use a pre-amp...

2) Use an antenna with higher gain in the frequency you're having trouble with. (For upper UHF stuff an antennas direct 91 XG has very high gain, depending on what he's trying to pull in there might be a better option than the DB8)

Any ideas what we did wrong?
You need to make sure they are in phase, both Baluns must be installed the same way. The front of the balun box has to be the same direction.
Also, bothe antennas have to be assembled the same, if one is up-side-down, they cancel each other out, especially in the forward direction.
Good Luck.

The C5 has some UHF gain (about 5 dbi). If it is "stacked" with a 91XG, would the UHF gain of the C5 help the UHF gain of the 91XG? Or does the 91XG gain simply override/cancel/replace the UHF gain of the C5?

No. Use each antenna for its best performance characteristics, that is, the C5 for high-VHF and the 91XG for UHF, combined with a UVSJ or a preamp that has separate inputs.

You need to make sure they are in phase, both Baluns must be installed the same way. The front of the balun box has to be the same direction.
Also, bothe antennas have to be assembled the same, if one is up-side-down, they cancel each other out, especially in the forward direction.
Good Luck.
Hi, Thanks for all the replies!! The phase seemed to be the problem. We turned the bottom antenna upside down, and now it seems to be back. What we were trying to do is avoid the drop-outs he has. Normally WGRZ and WIVB come in approx 80%. But there is times where it will drop out to zero for about 5-10 minutes, and then inexplicably be back at 80% (Signal Quality). We are using a 7777 pre-amp set to Separate with the FM Trap on. Only the UHF is plugged in and we put a terminator on the VHF port.

With two antenna's, we have noted most channels have a higher Signal quality, however, some have completely dropped out (57 UHF, and 44 UHF). Consulting with Antennas Direct they mentioned that having a second antenna can create "Nulls", where certain frequencies are completely blocked out. 57 and 44 are local from downtown TO, so this could explain. Not a big deal as who watches these anyway...

So I have read here that stacking antennas only adds 3 or so DB. Does this include the insertion loss for the combiner? Or does that reduce it more. I have seen some old stacks done years ago with twin lead.The 2 are connected together by running the wire from ant. teminals strait down (not over to the mast) to ant. terminals then splicing in at the mid point. No combiner. Can that work?

some have completely dropped out (57 UHF, and 44 UHF)....
57.1 now broadcasts on RF channel 44. You need to do a re-scan. Not just an add on scan, but a full re-scan.

So I have read here that stacking antennas only adds 3 or so DB. Does this include the insertion loss for the combiner? Or does that reduce it more. I have seen some old stacks done years ago with twin lead.The 2 are connected together by running the wire from ant. teminals strait down (not over to the mast) to ant. terminals then splicing in at the mid point. No combiner. Can that work?
NOT very well, as evidenced by "horizontal stacking" two 4-Bays into an 8-Bay:
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html

It's a miracle when combining DOES work:
Stacking identical antennas can achieve up to 3 dB Gain,
MINUS 0.5 Insertion Loss in the Combiner,
MINUS Loss due to Amplitude and Phase mismatches within the Combiner,
MINUS Antenna Gain and Phase mismatches,
MINUS Amplitude and Phase mismatches due to signal variations between the two Antennas.

Combiner Loss Tests (divide by two): http://www.antennahacks.com
Hybrid Combiner Equations: http://www.rfparts.com.au/public_html/appnotes/pdffiles/43846.55602.1443.17591/m568.pdf
Antenna-to-Antenna Variations: http://www.hdtvprimer.com/ANTENNAS/siting.html

Yeah, the antennas were the wrong distance apart (too close?). I'm not sure what the general consensus is on vertical separation for DB8 stacking, maybe somebody can confirm?

for the somewhat similar channel maste 4228, the feeling seems to be that you the distance between the top bowtie of the lower antenna and the bottom bowtie of the upper antenna should be twice the spacing between the bowties on the antennas