[BC] IBOC on AM is good.

[PeterH]

On Nov 19, 2010, at 11:09 AM, Alex Hartman wrote:

> I've got an array that i've recently acquired that's quite  
> entertaining. 4 AMs multiplexed onto 7 towers. Quite the feat.

Yes, indeed so.

Honolulu has quite a number of multiplexes, perhaps including two  
into which are four frequencies, each, and several others which have  
fewer than four frequencies, each. But, all of those are ND-U ...  
quite different from that which you describe.

Power is somewhat limited, with some stations, the "legacy" ones,  
running 10 kW into what was formerly a 5 kW tower, but with others  
limited to between 5 kW and 10 kW, 7.5 kW in some cases.

I have yet to hear of a five-plex, however.

Boston has a recently accomplished triplex, done using MoM, which  
uses the site of 1600, but none of its original towers, and now has  
five new towers, in an almost 2 x 3 = 6 configuration, but with the  
lowest-powered tower deleted.

"Optimization", as implemented in the 1969 IEEE Transactions on  
Broadcasting issue, allows for very great freedom in most array  
parameters, including the possibility of assigning almost 1.0 field  
ratio to all or almost all towers, thereby completely avoiding the  
pathological cases of Fibonacci field ratios, such as 1, 4, 6, 4, 1  
(for five towers) and 1, 5, 10, 10, 5, 1 (for six towers).

(Of course, seven in-line towers has never been implemented, although  
I have no doubt that it may have been applied-for, in at least one  
case).

Still, 1, 3, 3, 1 has proven to be stable in at least one case, and  
most probably others.

>
>>> WNYC, now on 820, is diplexing into WMCA's three towers.
>>> Historically, when on 830, WNYC had its own array.

I believe WNYC's original 830 array was co-located with 1560, which  
may be why 1560, in Queens, has four towers on-site but it actually  
uses only three of the four towers, two days and three nights, and  
one of the four towers is unused during all hours. All are 171  
degrees tall on 1560, which is 90.99 degrees on 830. Ideal, really,  
for both frequencies.

Its 820 array is diplexed with WMCA/570, with 10 kW/1 kW for WNYC and  
5 kW DA-1 for WMCA.