Eric Lemmon wrote:
>
> Joe,
>
> The latest RFS/Celwave catalog identifies the 200-series antenna as
> the "Stationmaster II."
I wonder what is different about it. I also wonder how you tell the
difference since both are PD200s (or is there a new suffix added?)
> While a PD-200 ordered with a center frequency of 145.06 MHz will
> probably do very well for a 2m repeater operating at 145.360 TX and
> 144.760 RX, it will NOT do well for a repeater operating at 147.300 TX
> and 147.900 RX. That was the point I wanted to make;
And I'm perfectly willing to concede that point. I was going by ordering
one in which case you would know the frequencies. I also would rather
have it cut for the TX since that's where the SWR is the most critical,
as opposed to having it cut for the 'average' frequency (half way
between the input and output). Actually, if you have it cut for 147 MHz,
you can cover virtually the entire 146-148 MHz segment (assuming using
LIHO on 146 and HILO on 147 MHz). Granted, the spec would be
146.25-147.75, but the RX doesn't care as much about the specs.
the PD-200 has a
> very narrow bandwidth that does not cover the entire 2m band, and it
> must be ordered for the specific repeater pair desired. For this
> reason, a PD200 antenna ordered for service on one 2m repeater pair may
> be useless for service on a different 2m repeater pair.
That's where proper coordination comes in. I know of two 2M repeaters
that have ever had to change frequency (both due to lack of
coordination) back in the 70s. IOW, the chances of having to change
frequencies is rather remote. If it's a new repeater and you don't know
the final frequency, put up a ringo or something to get you by until you
do know the final frequency. After all, the same can be said for
duplexers and crystals. Both of those are much more frequency specific.
Granted, recrystalling elements isn't that expensive, and retuning a
duplexer is not hard as long as you have the right equipment. Still,
it's best to order such items on-frequency.
> On the other hand, the PD220-2 "Super Stationmaster" covers the entire
> 2m band and can be used on any repeater pair within that band with no
> concern about specific frequencies. You are absolutely correct in your
> observation that the gain of the PD220-2 (and similar antennas from
> other manufacturers) is derated to 4.8 dBd due to length constraints.
> However, in practical terms, this gain reduction is irrelevant.
Technically, I would agree. 0.45 dB is nothing in the grand scheme of
things where it takes 3dB to notice any difference. BUT, how many people
would take an extra 10W on their power output if they could? How many
would take a 10W power cut and a .01 uV hit on their RX? And, if you
know the operating frequencies, and they are going to be fixed for a
while, why accept any loss? :-))
Personally, I would go with the open dipole type. I've seen too many
repeaters with noise problems using Stationmaster and SuperStationmaster
type antennas. They flex too much at VHF to maintain the physical
integrity of the element connections. I also know of a club who replaced
their PD200 (or 220) with a Hustler G7 (it was a G7 or a G6) and lost 3
dB of real world signal strength despite the higher gain spec. They just
wouldn't believe that the Hustler would be that much worse. Now they
know. But, on the bright side, their duplex noise is gone.
Joe M.
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