Paul, I like DB antennas also. Their duplexers are also excellent. Excellent company.
I do like the DB224, and other exposed dipole antennas, for it performs very well (the specs are real) and is flexible...one can adjust the pattern for what one needs. Mine has its main lobe at 135 deg which is to down town Tampa about 30 miles away. Don't need much coverage into the Gulf, hi. The 1300 ft tower does get lightning obviously especially since we are in lightning capital of the US. It gets struck directly a number times a year. However, we have had no problems being side mounted. I am just concerned with the salt air. I definitily know the exposed dipoles have a life problem with it. We've seen too many of them in this condition here. The main problem has been with the connections and harness, not the dipoles themselves although I've seen some pretty ugly ones. Coating the whole antenna is a thought, but really don't think necessary for only the connections and wiring harness have shown problems. My problem is not static. I mentioned static with a fiber glass pole having only a lower mount. The problem now is 2:1 SWR on the ground and noticable less coverage. The antenna or crossband coupler is bad...bet the antenna is the problem. I am sure it could be repaired unless one or more of the elements are gone. But again I know the salt air is a problem. Maybe I could get a fiber glass radome for the DB224. TV broadcast stations do this, hi. 73, ron, n9ee/r >From: Paul Finch <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 10:21:14 CDT >To: [email protected] >Subject: RE: [Repeater-Builder] DB224 Survival in Florida >Ron, > >I can't stress the importance if tightening ALL of the hardware on the DB >antennas, they were built for the low mount and top of tower installations. >It sounds like loose connections from the factory is what your static >problems are. I can't tell you the number of antennas I have prepared that >seemed to have hardware only finger tight. > >Scotchkote is dark brown and so far is the only thing I have seen that >stands up to Texas Florida Sun. Careful, if you get it on your skin you >have to wear it off or use MEK. > >Remember, lightning will exit a tower usually around 150 feet down from >where it strikes the tower and can wipe out fiberglass antennas even when >side-mounted on a tower. I will say that I have some fiberglass antennas on >my 500 foot towers but in every case there are DB folded dipole antennas >above them. > >I am about to raise a TXRX broadband 860-930 MHz 4 degree down-tilt antenna >to the top platform to replace a DB-806 that was used by a old paging >company. That will be my receive antenna for the 900 MHz Ham repeaters. >That antenna at $1,400.00 would be a very expensive lifetime supply of >toothpicks if hit by lightning. It will almost be surrounded by folded >dipole antennas. Will also be raising another DB-420 antenna to the 400 >foot platform for my second transmit combiner. > >It sounds like the guy that mentioned coating the whole antenna may have a >good idea but I would also coat the connections with Scotchkote beforehand. >I never found anything that I thought would stick that well to aluminum that >you could coat the whole antenna with. > >As you can tell, I like DB antennas, just think they need some quality >control or at least someone that has strength enough to tighten the screws >the way they should. > >Paul > >-----Original Message----- >From: [email protected] >[mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright >Sent: Sunday, September 02, 2007 6:24 PM >To: [email protected] >Subject: Re: [Repeater-Builder] DB224 Survival in Florida > >Paul, > >Prior to putting up our DB224 we coated the connections with a commerical >coating for antennas. It was from a local broadcast station who uses it. >Not sure if same 3M product you mentioned. It was gold in color and really >stands out on the antenna. This has been done on a number of exposed >dipoles like the DB408s here and it last less than 10 years, some as short >as 6 years. > >I like the DB224, but do not trust it for the salt air and will go with a >RFS/Cel Wave 200 with both a bottom and top bracket. > >Another problem with these is with mounting only at the bottom and they do >not like waving the wind. We had another UHF system install a new one and >from the start static when windy. A top bracket solved the problem...this >goes back about 4 years and it is still in service and is about 1/2 mile >from the salt water. We did the same for the DB224 install. > >Thanks for the info. I am sure many here can use the experience and advice. > >73, ron, n9ee/r > > > >>From: Paul Finch <[EMAIL PROTECTED]> >>Date: 2007/09/02 Sun PM 04:55:00 CDT >>To: [email protected] >>Subject: [Repeater-Builder] DB224 Survival in Florida > >>Ron and Eric, >> >>I emailed this out before, here goes again. I learned all I know about the >>DB antennas from two of the engineers that designed the antenna many years >>ago. My Boss at the time was a personnel friend of one and the other ended >>up at Wacom where I did a lot of business with him. I have a lot of >respect >>for both. >> >>First, when you get a DB folded dipole antenna, disconnect all connections >>at the dipoles and tighten everything and put it back together. After >that, >>put as many coats as you can of Scotchkote from 3M on every connection, >>especially if dissimilar metals are present. Coat every knot, terminal and >>joint on the antenna with Scotchkote that you can. Coat the whole thing if >>you can. That keeps the salt from getting to those parts. Do this and the >>antenna will last much longer and outlive the fiberglass antennas every >>time. >> >>I was Director of Field Engineering for a nationwide paging company, we had >>a office in Tampa Florida and all we used were the DB-224 antennas. I >>threatened to fire anyone that put an antenna in the air without tightening >>the connections and sealing it first. Never had to fire anyone over that, >>they knew how important it was to me. >> >>We still had a few problems mainly from the first batch of Phelps Dog >(Dodge >>aka Celwave aka RF Industries or whatever they call themselves now) >antennas >>we put up. The difference between the folded dipole antenna and fiberglass >>radome antennas in lightning was not worth the chance in a emergency >system. >> >> >>Hope this helps, >>Paul >> > > >Ron Wright, N9EE >727-376-6575 >MICRO COMPUTER CONCEPTS >Owner 146.64 repeater Tampa Bay, FL >No tone, all are welcome. > > > > > > > >Yahoo! Groups Links > > > > > >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.5.484 / Virus Database: 269.13.2 - Release Date: 9/1/2007 12:00 >AM > > >No virus found in this outgoing message. >Checked by AVG Free Edition. >Version: 7.5.484 / Virus Database: 269.13.2/985 - Release Date: 9/2/2007 >4:32 PM > > > > > > > > > >Yahoo! Groups Links > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
