I installed a 91XG/STM1000 on the parsonage of church where I grew up, but I don't have a photo of it. if I get back there soon and remember it, I'll try to snap a photo of it.

ADTech -- thanks a million!
it's always good to see how others "did it" and i'm sure your pictures will be of great help!

now i can order that 2nd stm-1000 and get a 2x4 to build proper anchoring for the j-mount.

cheers.

I've been pitching an inexpensive "universal" add-on that can be bolted to the back of any of our panel antennas. The parts look like this:

http://www.digitalhome.ca/forum/showpost.php?p=1343542&postcount=294

I have no idea if it will actually come about. It's pretty simple - just a dipole w/holder, a diplexer, a couple of cables, and some hardware.

Any luck getting this as a product? There would be demand for a small, inexpensive, outdoor VHF-HI antenna. Even the C5 is bigger (and more expensive) than many need. As I said before, it would optimally be mast mounted, but the current mount would be better than nothing (end user could always attach it to a U-Bolt nest).

ADTech: I've been pitching an inexpensive "universal" add-on that can be bolted to the back of any of our panel antennas.

I have this VHF add on and, at least on the one I received, the balun is the best I've come across yet. It may be just the luck of the draw but the loss on this balun beats everything else I have (ChannelMaster, Winegard, Radio Shack, PVMT2 and an assortment of others).

There's no visible branding on the balun so it may have just come from a good batch from who knows where.

Roger,

No plans to offer it as a stand-alone product. However, one can take a C2 VHF upgrade kit and take it apart for its components. Judicious use of a drill and or a hacksaw (when necessary) plus a few zip ties can yield a surprising variety of options for a DIYer. It also includes a mast clamp mount!

These kits have been ordered by the GTA dealers (listed on our website) including forum sponsor SnR in the past so they may be readily available to Canadian customers.


Bob,

Those baluns tested out pretty well. Visually, they appear to be identical to the units previously supplied by Summitsource as item # COPBAL. Item appears to be discontinued now from that vendor.

Hmm. Strange. I found on your website by Googling the C2 VHF Reflector Assembly (http://www.antennasdirect.com/store/uhf-vhf.html), but it doesn't seem to be listed as one of your VHF antennas. I thought the only way to buy the VHF element was to buy an entire C2V. This upgrade kit is a much more reasonable option.

I would also like to see a reflectorless C2, but that is probably easy enough to make just by removing the reflector from the current C2.

Hello,

I don't see the DB4e on Stampeder's antenna chart. Two questions:

1) Is it not there because it hasn't been tested / evaluated yet?
2) Can it be assumed that it is equivalent in performance to the DB-8 which has great rankings?

Thanks!

interdit_450, the DB4e is a good antenna, but I am not sure if you are getting good value for money. It cannot be assumed to be equivalent in performance to the DB8, but instead performs somewhere between a DB4 and a DB8.

Actually, IMO I have had both antenna's and believe the DB4e to be really close to a DB8 in performance. The DB4e has a better front to back ratio as tested in real application from my home here in London, On.
My biggest issue regarding these two antenna's is the side lobe reception. It is too good for my application here in London as co channel is havoc during tropo. The DB8 was just as bad. This is the main reason I took down my DB8 and put it up at my father's house.
Now I still have yet to take down my DB4e that I installed months back and put back up my 91XG which is really the king around here.
Another point I have noticed that channel's below let's say RF30 favour better reception form the DB4e and above this the 91XG is better.
If antenna footprint, wind load, price and the character's mentioned regarding channel's below RF30 are desirable you cannot go wrong with the DB4e.

I was basing my opinion on the thread DB4e vs. Stacked 4221HD's - the results (http://www.digitalhome.ca/forum/showthread.php?t=148377). Interesting about the f/b ratio. I wonder if that has to do with the shape of the screen.

The DB4e will have a much wider beam width (not lobes) as it is a single stack. A DB8 has a much narrower beamwidth due to phase interference between the two stacks for off angle signals. Its side lobes are where the phase shift gets close to 360 degrees and starts to add back together again. The 91XG has a similar beamwidth as the DB8, but it doesn't have the big side lobes the DB8 has, so it doesn't surprise me that it solves co-channel interference issues.

The 91XG is still using an old design that was optimized for use up to channel 69, and since Yagis have a sharp drop above the target frequency and a gradual drop below, it doesn't surprise me that it is better for the higher channels but the DB4e (which is optimized for the reduced UHF band) is better for the lower channels (bowties have a flatter response curve).

Roger,

The C2 VHF Upgrade reflector assembly is listed only as an accessory on our website. Shop Now > Accessories > Reflectors.

Good comments by all regarding the DB4e, DB8, and 91XG. All are spot-on. DB4e will have forward peak gains close to a DB8 but with the wider beamwidth of the 4-bay. A fair compromise for some locations, not as good for others.

Please note that formal data sheets for the DB4e and 91XG are on our website. Just go to the individual product's web page and click on "Documents". Regrettably, no such data sheet has been compiled for the DB8 or the C4 and I don't expect one will ever be done for the DB8. The formal data sheet for the C4 is on our engineer's "To do" list, but it's a low priority for his time.

Cheers!

The formal data sheet for the C4 is on our engineer's "To do" list, but it's a low priority for his time.

I'll just chime in with an observation based upon a smattering of measurements done here over a period of a year or so. The C4 is most "predicable" of the group (91XG, DB4e and DB8) that I have on hand. By that I mean the gain seems the flattest across the 14-51 spectrum (all of which we have here in the Dallas-Ft. Worth market). The others have hot spots at certain frequencies in contrast to what I've seen with the C4.

interdit_450, the Antenna Chart has gone through many revisions over the past 7 years and is continuing to evolve. As more and more evidence comes forward about today's antennas I update or change the evaluations accordingly. AD has every right to be proud of the DB4e so I am like a sponge, soaking up everything I can about it's performance in comparison to other "benchmark" antennas.

AD Tech

In the Amplifiers thread I have posted some questions about pre-amps desgined for areas with a combination of strong and weak signals.

It starts with post 3075. I have asked about the Antennas Direct PA19 pre-amp.

The write-up for the PA19 on the AD website is intriguing for me because I want to replace my pre-amp this summer.

One extra question I have about the PA19 that does not apply to the Winegard or Antennacraft pre-amps, is what size mast can the PA19 be attached to? It seems like the plastic molding on the PA19 is only designed to fit one size mast. Is this true?

Bob,

The C4 has a gain vs frequency curve that is relatively flat across the design band of 14-51. We print a graph of it and of the VSWR along with a channel 51 polar plot on the back of our current C4 boxes. I'll see if I can get them added to the website as an interim measure and in lieu of a formal tech data sheet.

Here are the plots which show calculated gain and VSWR vs frequency along with channel cuts for 14, 33, and 51:


http://dl.dropbox.com/u/23201192/ClearStream4_Dir%26VSWR_vs_Frq.jpg
http://dl.dropbox.com/u/23201192/ClearStream4_Horiz_Plane_Pat_Ch14.jpg
http://dl.dropbox.com/u/23201192/ClearStream4_Horiz_Plane_Pat_Ch33.jpg
http://dl.dropbox.com/u/23201192/ClearStream4_Horiz_Plane_Pat_Ch51.jpg

HWP,

The CPA19 will fit on a mast as large as 1.75" in diameter.


Stampeder,

Glad to see you back!


Cheers!

ADTech, I just wanted you to see what kinds of crazy things people are doing to your "children"...

http://www.digitalhome.ca/forum/picture.php?albumid=880&pictureid=5333

I was trying to use stagger-stacking to cancel out an offending co-channel from behind. It didn't work beacuse the power difference between the two stations is just too great, but the exercise did produce a big rear null on the target frequency and several stations a few channels away.
I'll say this about a pair of C2s (or a taken-apart C4)- they are great for experimenting with special combinations like stagger stacks and the "two-antenna trick" described on HDTV Primer.

^^^lithOTA, it may be just the angle the picture was taken at, but it doesn't look like the 2 coax feeds are the same length. Was this intentional? Normally you would want them the same length, unless they are carefully measured to phase shift one antenna, but I don't know why you would do both that and a stagger stack.

The two lengths of coax must be different for stagger stacking to work properly.

http://i496.photobucket.com/albums/rr328/rabbit73_photos/staggerstacking_1.jpg

I quote from pages 186-187 of TV Antennas and Signal Distribution Systems by M. J. Salvati:

"Stagger stacking is a special variation of vertical stacking in which one antenna is mounted one quarter wavelength ahead of the other (Fig. 8-8). The cable section connecting the forward antenna to the signal combiner is made an electrical quarter wavelength longer than the other so the signals from the front are combined in phase. Signals arriving from the back, however, are 180 degrees out of phase and thus cancel. This results in a very high front-to-back ratio, even if the front-to-back ratio of the antennas is very poor. When this technique is used on antennas having a high front-to-back ratio to begin with, the rearward pickup of the array is virtually zero."

I think lithOTA did a good job of using what he had on hand to make a valid test.

Well done, Mike!

^^^Oh, OK. That makes sense! Wouldn't you need to compensate for the velocity factor of the coax when making it 1/4 wavelength longer though? I guess that is what they mean by electrical quarter wavelength.

ADTech, I just wanted you to see what kinds of crazy things people are doing to your "children"...

Well, I'm more a "step-uncle" for most of these things... I'll show your photo to the "Daddy", he'll get a kick out of it.

Pretty cool!