On Sat, 9 Jun 2018 18:02:00 -0700 (PDT), Phil Allison
wrote:

wrote:
I want one with continuously variable IF bandwidth on the front.

** Such a feature is useful with AM reception but not with broadcast FM.
The FM signal is inherently wide band, with +/-75 kHz deviation at peak audio level - if the IF bandwidth is less than 150kHz, distorted sound is the result.
I have a radio scanner ( AR 1000xlt ) with wide and narrow FM modes, 30kHz and 200kHz respectively. Listening to broadcast FM while in narrow mode is *intolerable*, in wide mode it sounds just fine.
.... Phil

A bit of hair-splitting here. The FM channel allocation in the USA is
at 200 KHz intervals. However, if one adds the digital (HD Radio,
IBOC, iBiquity, etc) modulation, the bandwidth is now 400 KHz wide:
https://en.wikipedia.org/wiki/In-band_on-channel
This is what it looks like on a spectrum analyzer:
http://www.learnbydestroying.com/jeffl/crud/KBRG-100_3.jpg
http://www.learnbydestroying.com/jeffl/crud/KCSM.jpg

In most HD Radio receivers, the IF bandwidth is set by a digital
filter. For conventional FM, it's 200 KHz wide. For digital FM, it's
400 KHz wide. I suppose it could be front panel set by the user, but
methinks it makes more sense to have the IF bandwidth automagically
set by the mode and sub-channel.

Measuring Your IBOC Spectrum
http://www.nautel.com/wp-content/uploads/2011/08/NAB-Measuring-Your-IBOC-Spectrum-David-Maxson.pdf

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558