@fybush
Scott wrote this on the Boston Radio Interest mailing list - I am reposting it here simply to share his expertise on the subject.
[Boston-Radio-Interest] WJIB applies for 720
Let me try to clarify (as best I can) somethe subject. of the questions that have
come up about what might be in the works for WJIB - and please note that
this is all informed speculation on my part, because I'm not involved in
whatever John G and Dennis Jackson have up their sleeves.
The AM side of things first:
There are two different ways things can go for WJIB once it's granted
its move from 740 to 720, assuming it can't stay indefinitely at the
current Concord Ave. site.
If the goal is simply to move to a similar non-directional facility, the
options are limited. While a non-directional AM is by far the easiest to
build out, you can look at the filing for 720 from Concord Ave. to see
that a ND signal can't be much more than 1000 watts by day if it's going
to be able to protect WACE Chicopee on 730 and WOR on 710. Same with the
13 watts at night and WGN and the ghost allocation for CHTN.
If WJIB is to remain licensed to Cambridge, it has to put 5 mV/m over
most of the city of Cambridge by day, and that further limits the sites
where it might diplex or triplex. As others have noted, several sites
are either gone or going - the old 1510 in Waltham, the WBZ aux tower in
Allston, the old WILD 1090 in Medford, and soon the 1430/1090 site
nearby. For a station as low on the dial as 720, you also need a
relatively tall tower for efficiency and to control skywave takeoff
angle, which might make the 1150/1470 site in Arlington challenging, too.
The FCC's rules do allow WJIB to leave Cambridge behind as a city of
license, since Cambridge is part of the larger Boston urbanized area. So
if a site change means Cambridge won't get 5 mV/m of signal but the new
signal will cover, say, Somerville or Everett or Chelsea, that's a
possible COL change.
There is, however, a second possibility. Let's not forget that
Garabedian started the long process that turned the old WGTR 1060 from a
suburban non-directional daytimer in Natick into a much larger (partial)
metro signal, which in turn also spawned the current 890. With the use
of a multiple-tower DA, WJIB on 720 could theoretically go somewhere
southwest of Boston and aim a more powerful signal north and east over
Boston while still protecting WACE and WOR. (Someone here noted that a
similar proposal was floated on 740, with a COL of Needham, before Bob
owned the station.)
There are a few possible sites for such an operation, including the old
WKOX 1200 towers in Framingham (later used by WRPT 650 and now dormant)
and the 890/1060 site in Ashland. I haven't done the research to see if
the number of towers, height and spacing at either of those sites would
provide any kind of viable pattern on 720. And then there's the matter
of cost: especially at the 890/1060 site, adding a third AM station
increases the cost immensely, since the accept/reject networks and
phasors for a triplex are complex. It could easily cost into the high
six figures for a project like that. Is it worth it just to get, say, 10
kW by day and 1000 watts at night in a narrow beam aimed over Boston? At
some point, you reach a threshold where it's probably cheaper to go to
Audacy's bankruptcy trustees and just buy 850.
(As a minor change, which is the only change the FCC will grant, a move
to a higher-powered DA site would still require a showing of overlap
between the new 5 mV/m signal and the 5 mV/m day signal that WJIB will
have on 720 from Cambridge. That somewhat limits how far west you could
go with a move.)
It may well be that John and Dennis have a plan here that I haven't
figured out yet, but it's hard for me to see how a high-power DA move
like this would pay off.
As for the FM translator, it's limited to the north by WGIR-FM, to the
southwest by the WMRC translator in Milford and now to the southeast by
the new WFNX-LP 101.3 in Scituate and WMEX's 101.1 translator.
However, it can still be improved considerably if it moves from Concord
Ave. I *do* have some firsthand knowledge of this one, because I was the
engineering consultant who put the 101.3 application together for Bob a
few years ago. We knew that 101.3 would have been a much better signal
if it went up higher, but Bob understandably didn't want the expense of
a lease on the Pru or Hancock.
Here's a weird thing about translators and ONLY translators: unlike all
other FM services, there's no height limit for translators. They can be
up to 250 watts ERP at any height at all, and they don't get derated in
power the higher they go. Out west, there are translators on
mountaintops in places like Albuquerque that actually have more power
than a height-derated class A (6 kW) FM would be allowed to use!
So, IF John G wanted to work out an arrangement to get the 101.3
translator up high on a skyscraper roof or one of the tall TV towers, it
might take a directional antenna to limit interference toward WGIR and
the other 101.1/101.3 translators, but over the city and nearby suburbs
the signal strength on 101.3 would be much better than it is now from
Cambridge. It's still never going to be a full-metro signal, but it can
improve! (There's not really an option to buy another translator - the
sale of the 94.9 and 96.5 signals claimed the last of the currently
available ones out there.)
I am very much looking forward to seeing what Dennis and John end up
doing. They're among the smartest radio people I know, and they deserve
our patience and some amount of privacy while they get it all figured
out. Once they've assembled all the moving parts, we'll know soon enough.
Finally: yes, the shifting AM frequencies will affect DXers. I grapple
with this often as I'm working on station moves for my clients, knowing
that I'm not making friends in the DX community with those added
signals. But that's been the paradox of the DX hobby for a century now:
as with trainspotting, it's a hobby that exists at the edge of a
business that doesn't really cater directly to it. As DXers, we take the
signals that are out there and do our best to find something new and
interesting to pick up as the signals around us change. I'm sure TV
DXers in 1957 were just as annoyed to lose reception of New York or
Bangor on channel 5 once Boston began using the channel!
Happy to try to answer whatever questions I can...
s