900 MHz antenna question
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kf4sqb
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900 MHz antenna question
Does anyone know of a 900 MHz antenna made in the same "style" as the DB224? If so, where would I find one?
brett "dot" kitchens "at" marel "dot" com
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
I have not seen any folded dipole antennas for 900 lately...pretty scarce.
Most are closed, collinears due to the feed impedance and weather protection required, but you can buy a DB812 series, they make them (or used to) to cover the high end of 800 through 900, or you could get one that I used to have(two) that went from 806-902....but they are H E A V Y buggers....about 50+ pounds and @15' long(tall) too.
Think a 3-1/2" O,D as well, with a 2' aluminum mounting area at the bottom.
Drains on both ends for inverted mounting(cell sites).
Type 'N' connection in the base...Corporate feed structure for equal distribution of RF throughout the antenna.
Did I say it was heavy?
Most are closed, collinears due to the feed impedance and weather protection required, but you can buy a DB812 series, they make them (or used to) to cover the high end of 800 through 900, or you could get one that I used to have(two) that went from 806-902....but they are H E A V Y buggers....about 50+ pounds and @15' long(tall) too.
Think a 3-1/2" O,D as well, with a 2' aluminum mounting area at the bottom.
Drains on both ends for inverted mounting(cell sites).
Type 'N' connection in the base...Corporate feed structure for equal distribution of RF throughout the antenna.
Did I say it was heavy?
The DB products model DB-812F-X is of the corporate feed structure and works great from 806-901 Mhz. with very little loss and high gain as well, thanks to the dipole design and feed.
I used several of these very antennas in the 900 ham band in the past when I obtained 10 from a carrier I used to work for.
We had all of them struck several times by lightning with the brass tip melted all over, but only a single antenna that was TDR'd showed any loss above what could be considered 'normal'.
Corporate feed is far superior to using external phasing harnesses, especially at higher frequency ranges such as 800/900.
This is why you rarely see any exposed dipole antennas for 900 Mhz, the losses are too great once you add dipoles to the 'array'.
UT-250 by Uniform Tubes is a great mini-hardline, and the DB-812 used several feet of it, as well as a matching 'stub' of tuned line.
They were also used as 'null fill' antennas at cell sites and served that duty excellently as well due to the two drain caps on this model and others, so you rarely had to worry about water ingress that could build up and corrode the internal network.
Crack open a good quality fiberglass antenna built for 900 Mhz, I doubt you'll see ANY coaxial phasing harnesses, but I'll be willing to bet you WILL see the same corporate feed, it's just the most efficient form of internal element matching for UHF and above.
Junk fiberglass models will have a simple wire/coil design like those Diamond antennas and so on, but the good ones will more than likely have a D.C grounded system that is of the corporate feed design since the single input feeds all elements equally, the gain is flatter across the band plus you get equal power distribution as well, including downtilt by either mechanical means or electrical, or none, depending on purpose.
I used several of these very antennas in the 900 ham band in the past when I obtained 10 from a carrier I used to work for.
We had all of them struck several times by lightning with the brass tip melted all over, but only a single antenna that was TDR'd showed any loss above what could be considered 'normal'.
Corporate feed is far superior to using external phasing harnesses, especially at higher frequency ranges such as 800/900.
This is why you rarely see any exposed dipole antennas for 900 Mhz, the losses are too great once you add dipoles to the 'array'.
UT-250 by Uniform Tubes is a great mini-hardline, and the DB-812 used several feet of it, as well as a matching 'stub' of tuned line.
They were also used as 'null fill' antennas at cell sites and served that duty excellently as well due to the two drain caps on this model and others, so you rarely had to worry about water ingress that could build up and corrode the internal network.
Crack open a good quality fiberglass antenna built for 900 Mhz, I doubt you'll see ANY coaxial phasing harnesses, but I'll be willing to bet you WILL see the same corporate feed, it's just the most efficient form of internal element matching for UHF and above.
Junk fiberglass models will have a simple wire/coil design like those Diamond antennas and so on, but the good ones will more than likely have a D.C grounded system that is of the corporate feed design since the single input feeds all elements equally, the gain is flatter across the band plus you get equal power distribution as well, including downtilt by either mechanical means or electrical, or none, depending on purpose.