DB420 vs. DB408 in flat terrain

[n4dbm]

Greetings,
I know how to do the math and I am fully aware of how a 3 dB change doesn't make a very noticeable difference in the field, but I need some real-world experience. I have played with UHF power amplifiers, going from 50 watts to 100 watts for example on this station is certainly not worth the effort when it comes to my observations out on the road while working the repeater.

I have a DB420 at 150 feet, top mounted, up in the clear, with very flat terrain. I am used to the coverage area, know where it gets noisy and where it stops.

The aging DB420 from the late 80's has finally developed duplex noise, probably a joint going bad. I am all about reducing wind-load on the tower. I have a new DB408 ready to go, which, in lab conditions has 2.6 dB gain less than the DB420.

My common sense and rational mind say that losing 2.6 dB will be a very slight, detectable difference on the road out in the field, but my memory from 20 plus years ago when I did this same change on another repeater tells me different. It "seems" to me the DB420 worked much better than the 408, despite the figures that say in all reality, it shouldn't. Maybe psychologically, all the effort 20 years ago to change the antenna to one "twice its size" made me at least think it was performing better, but was it all in my mind?

I need real-world experience input from anyone who has changed a DB408 to a DB420 (or the other way around) and tell me your observations. Thanks much.

 

[buddrousa]

Go back to the DB420 the DB408 is just a control antenna. Your pattern now with the DB420 will change drastically if you put up the DB408.
3 DB doubles power and signal.

 

[n4dbm]

Go back to the DB420 the DB408 is just a control antenna. Your pattern now with the DB420 will change drastically if you put up the DB408.
3 DB doubles power and signal.

What does "just a control antenna" mean?

What does "drastically" mean? To me it would mean 10 dB.. or going from 20 miles of range to 40 miles of range. The pattern from a 420 to a 408 goes from 7 degrees to 14 degrees of beamwidth. I understand how 3 dB doubles your power. I've doubled my power on the transmitter at this site before with very minimal difference (and a major pain in the rear). It's hard to believe that the difference between the two antennas would be all that much, but that's why I came here to ask for opinions, so thanks. Point considered.

 

[prcguy]

The difference between the antennas is noticeable, not drastic but noticeable. I've gone between a DB411 and DB413 which is a 3dB change and at a distance there was less noise and handhelds worked better on the bigger antenna.

 

[n4dbm]

The difference between the antennas is noticeable, not drastic but noticeable. I've gone between a DB411 and DB413 which is a 3dB change and at a distance there was less noise and handhelds worked better on the bigger antenna.

Thanks, that's what I was looking for. I've played with the 411 and 413 also (too bad the 413 is discontinued) not that I needed another one... but I've never compared one to another in the field from the same location.

 

[prcguy]

I spent some time here swapping antennas around on a couple of home repeaters and a DB411 greatly outperforms a Comet GP9 on UHF, both antennas tested in the exact same spot. I have a spare DB413 on the ground but chose to use a version of the DB413 on my tower that is split into two DB411s on the same mast. That way I can have an amateur and GMRS repeater and only use one precious antenna location on my tower.

Thanks, that's what I was looking for. I've played with the 411 and 413 also (too bad the 413 is discontinued) not that I needed another one... but I've never compared one to another in the field from the same location.

 

[buddrousa]

A control antenna is what I mounted at a BASE SITE that talked to a Repeater that also gave them fair range on DIRECT TALKAROUND Channels.