DB404-B antenna

[wqzw301]

Hello,

I have a DB404-B antenna. I was wondering if I can swap out the aluminum mast for a fiberglass mast (same Diameter).

The 2 bays of elements, coax and matching stubs are pretty lite on their own. So I'm not worried about stability...

Does the aluminum mast act as a reflector also? If it is a reflector, will the radiation patterns of each of the lateral dipoles, effect each other.

Is the aluminum mast just a mast or part of the antenna system?

Please and Thanks for any help

 

 

[gortex2]

Why would you swap it out ? Its much more stable with aluminum. Fiberglass will move around. 

[wqzw301]

I have a 40ft fiberglass mast. The aluminum pole is 15lbs. 

The fiberglass tubing is thick walled 1.75 od. But I can't attach an 18lb antenna (clamps, coax included) onto it.

So I though just attach the elements to the fiberglass and lose the heavy metal pole. 

I have a wide band Laird fiberglass antenna on the mast now... It weighs about 1.5lb. But would like the better reception of the folded dipoles.

[SteveShannon]

The comprehensive data sheet refers to the included mast as a reflector:

Quote

RF connector inner conductor and body grounded to reflector and mounting bracket

https://www.commscope.com/globalassets/digizuite/262253-p360-db404-b-comprehensiveexternal.pdf

Frankly, I think it's too much antenna to put on the top of a single 40 foot fiberglass pole that's 1.75", even with a heavy wall.  

[wqzw301]

Thanks

The elements are actually light, it's the pole that's heavy.

But the info you sent me,  says that it is a reflector and the elements are grounded to it.

So I'll save it for another mast, down the rode...

Much appreciated, thank you 

[SteveShannon]

1 hour ago, wqzw301 said:

Thanks

The elements are actually light, it's the pole that's heavy.

But the info you sent me,  says that it is a reflector and the elements are grounded to it.

So I'll save it for another mast, down the rode...

Much appreciated, thank you 

The elements are light, but they’ll have a wind load normal to the strongest axis of the fiberglass mast. A 40 foot fiberglass mast at 1.75 inches will be very flexible. Even just the elements would make the mast sway in the slightest breeze.

[JB007Rules]

I mean.... Just use guy wires no??  I have a DB404 as a portable antenna for my fiberglass system.... Never had an issue with it.  Here it is up at about 30- 32' or so to the base of the dipoles clamped 3 times without guys and also with guys (7 x 6' pieces with 18" inside the tube).  It's possible IMO but you need guys.  I'd say 3 at the top and 3 in the middle to be sure but I just did 3 at the top.  It's worth noting that as the suggestion of of Bob at TN076 engineering who is the maker of this set that you want to do 18" inside the pipe, not 12" with this heavier 404 antenna.  So you get about 32' with 7 pieces.  If you just did the 12" inside the tube you'd get 35'.

https://mgs4u.com/product/38-feet-heavy-duty-fiberglass-push-up-mast-mk-6-hd/ - this is what I have.

Hope this helps!

Thanks!

[SteveShannon]

36 minutes ago, JB007Rules said:

 

I mean.... Just use guy wires no??  I have a DB404 as a portable antenna for my fiberglass system.... Never had an issue with it.  Here it is up at about 30- 32' or so to the base of the dipoles clamped 3 times without guys and also with guys (7 x 6' pieces with 18" inside the tube). 

 

Absolutely he would need guys. But I understood him to say that he has a single 40’ mast that’s 1.25”. Maybe I misunderstood that, but if it’s true his entire mast will flex. Mid-guying would be necessary, but all guying increases the vertical load as well. 
You have a push-up mast that has a larger diameter base. So the bottom sections are much more rigid. 

[JB007Rules]

Good point!!  Mine of course gets skinnier the taller it gets!!