im sorry that i got this thread so far off course. i have not used a 420 my self, however i do have a 450-470 DB411 antenna (4 bay with all lobes facing the same way, each bay only has one dipole, looks like a 224 but for uhf.. the antenna is about 10-11 feet tall, and it works very well at 444/449. very low reflected power.. we swept the antenna with a site master and it swept well, though it was most resonant in the commercial band. if i can find the sweep ill post it. the DB antennas in the commercial split are generally ok to use in the near by ham band ive found.. it may not be ideal but it works well if thats what youve got.
ive heard of people putting "whiskers" on teh folded dipoles to bring the resonant frequency down a little by making the top/bottom of the dipole a little longer. ive never tried it and i dont know how it works. on the sinclairs.. those diploes are stood WAY off the mast... how are the standoffs connected to the mast? looks like a very heavy wind would twist them if they arent welded or keyed in some way. on the long long long antennas like the 224 and 420, we have found that they bend towards the bottom end at tropical storm force winds. part of the bottom of the mast is sleeved inside with another piece of pipe.. the bends usually occur where the internal sleeving stops.. andrews answer is to rate the antennas for a lower wind speed.. go figure. we have a site on a 1700 foor tower, equipment is at 1400, and theres an antenna at 1500 and 1600, or there abouts... they are 4 bay db vhf antennas, and they are top and bottom mounted.. thats why they dont bend. the bending we have seen were on buildings, where the antennas are bottom mounted only. in the event we ever had to install a new antenna for heavy duty use, i always thought id pull the short internal sleeve out and sleeve it all teh way to the top of the bottom section, with a heavier piece of aluminum pipe (it helps that we have an excellent aluminum distributor here). i guess thats all i have to say on antennas... oh yeah, and ge/ericsson/macom stuff is the way to go.. haha --- In Repeater-Builder@yahoogroups.com, "Nate Duehr" <[EMAIL PROTECTED]> wrote: > > On 4/30/07, Merritt <[EMAIL PROTECTED]> wrote: > > it was likely a lighter duty antenna... refer to the image below... > > > > http://sffma.net/images/147000/jan2006/DSC02920.JPG > > > > it may not even be sinclair.. if it isnt, who made it? > > Yeah, don't think that's Sinclair... but maybe something older... > those "wings" on the attach point don't look like anything I've ever > seen from Sinclair. > > If I can find a photo of the newer Sinclair ... hmm, let's see... > > <http://web.mac.com/wy0x/iWeb/Site/Squaw%20Mountain%20Trip%20-%20Fall%202006_files/DSCN0601.jpg> > > That's a crappy photo of way too much "stuff", but if you go straight > up the right hand tower leg in the tower closest to the camera, the > antenna at the very top, and the one on the side-arm way up there > pointed to the "right" in this photo both the HD UHF 4-bay Sinclair > types. > > On that same "right hand side" leg in this photo, side-mounted, is a > 4-bay VHF Sinclair HD model, also. The bottom two bays of the VHF are > kinda lost in the photo's clutter. > > You can spot the Sinclairs (and some DB's) because they use the longer > 1/2 wave spacing arms to get them away from their masts... for a > slightly different (usually more omni) pattern. It makes the VHF's > look like they're sticking out there a long way from their masts. > > The tower photo was taken more for it's "artistic" qualities than for > documentation, so -- it's not the greatest shot of any specific > antenna... > > For fun, this shot is from the "left" side of that same tower leg... > if you zoom it a lot, or look REAL hard you can see the buildings of > Downtown Denver in the right-center between the trees. > > <http://web.mac.com/wy0x/iWeb/Site/Squaw%20Mountain%20Trip%20-%20Fall%202006_files/DSCN0602.jpg> > > (God I love big mountains! Who needs voted receivers! GRIN!) > > Here's a pretty good shot of the SRL-114, their "cheap" non-HD type > older VHF array. I don't like these as much -- our club has one as a > "spare" VHF antenna in case of major damage where we need to get > something back on the air "quick"... > > <http://web.mac.com/wy0x/iWeb/Site/CRA%20Work%20Day_files/DSCN0554.jpg> > > This particular one was lying on my back porch there in the photos > last summer for some much-needed maintenance and cleanup. It appears > to still work "fine", I just don't really think it'd survive at most > of our mountain-top locations for long. > > And here's a couple of shots of a "newer style" Sinclair VHF 4-bay > from behind (its the VHF 4-bay on the first position inboard on the > right side near the tower). It's the non HD version, with an external > harness (another thing I don't like much in rugged environments a long > way from home).. > > <http://web.mac.com/wy0x/iWeb/Site/Cheyenne%20Mountain%20Summer%202006_files/DSCN0581.jpg> > > <http://web.mac.com/wy0x/iWeb/Site/Cheyenne%20Mountain%20Summer%202006_files/DSCN0584.jpg> > > And then, just for fun again... the shot of Colorado Springs from that site... > > http://web.mac.com/wy0x/iWeb/Site/Cheyenne%20Mountain%20Summer%202006_files/DSCN0600.jpg > > Nate WY0X >
