Review of Radio Shack Accurian 12-1686 HD receiver by Bob Foxworth - in 4 parts
begin part 3 of 4 AM HD. In Tampa there are two AM HD signals, on 820 and on 970. These are high power (daytime) signals located just a few miles distant from me. Both of these signals will decode to HD, at this close range. The big question of course is what is the limit of coverage at which the HD decode fails when analog is still usable. I am able to force a temporary un-lock of HD on these two AMs by just rotating the loop. There are two critical angles in which HD is marginal (even at this range) due to loop nulling. A nontechnical user who uses "set and forget" for his/her loop placement in the house runs a small chance of never hearing a desired HD AM, and may not understand the need for better loop placement, as the "collective experience" of outside antennas is now a lost art. When any non-HD frequency is tuned in, the display will say (for example) "860 AM". When tuning in, say 970, the display will pick up and show the call letter ID in a second, or even less than a second. It then takes 7 or 8 seconds for the audible decode to change to HD sound. When this happens,a HD logo becomes visible on the display, and a 6 line bar graph showing signal strength becomes visible. The bar graph is not rapidly responsive to input level changes (loop rotation, etc) and it is unclear what exactly drives it, as FM signals show most or all bars while AM show just some, and of course only on my 2 local HD signals. The main effect of HD is to brighten the high end audio response and to create a sensation of stereo separation. This effect is noticed best when the user is directly in front of the set (or using a headset) and is somewhat less pronounced when listening from a distance. The effect on WMGG (a Spanish music format) is quite a lot more noticeable than it is on WFLA (talk) where it is (to me) only somewhat apparent. The display latches the call letters which continue to show, even if the HD unlocks. WMGG has a scrolling line of text with their "megaclasica.com" web address. WFLA has no such data stream and the display just shows "artist: title:" in the area where the date and time, or scroll, otherwise appear. It's interesting to tune the set to 960 where the hiss is present on a dx398 etc, in this case a grinding bubbling type noise is heard, not too different than the analog case. (I'm sure someone is wondering about that). Incidentally WFLA hiss is somewhat louder on 960 than on 980 on an analog set. One of my plans is to determine the rough edges of the AM HD coverage. I would do this by taking the set in my truck, powering it from an AC inverter and setting up at various locations. I soon found that the inverter I have plays very badly with this (and probably other) sets, on AM, and this option is completely unworkable for me. I need to come up with a 5 VDC 5 A clean source. In the meantime I do have some results to offer. I set up the set at an indoor location in southern Pasco county, close to the intersection of SR41 and SR-54. Neither HD signal was even decently copiable in analog, let alone getting any HD. I need to go back and see if this is environmental. On the other hand I set up the receiver indoors at the K of C meeting hall on Fruitville Road in Sarasota, where WFLA gave just fragmentary bursts of HD. However I was surprised to see that WMGG gave a solid decode there. This is about 50 miles south of Tampa. FM usage is somewhat more satisfying. What is interesting to me is that the blend from FM analog to FM HD is hardly noticeable. It is more of a perception of a subtle difference, than the striking change I hear on 820 AM. The sound section of this radio, to me, is innately good enough that it renders analog FM quite nicely, and the program feed the FM folks use is not that much enhanced with HD. I had issues with decoding HD on a number of the FM offerings depending on how I placed the antenna, which one I used, and where I was in the house. The dipole needed to sometimes be fully extended and positioned, with placement issues somewhat like those for the AM loop. I am not a FM DXer and may not go a lot farther with this issue. Some FM customers will want the secondary programming which is available on FM. I won't do an exhaustive rundown of what's on the dial here as it won't help many in other markets. Non-comm WUSF is frequently but not always running separate programming on their secondary, which IDs as "WUSF eighty-nine seven two." They show as "89.7-1" or "89.7-2" when tuned in and the "new" station appears as if "dropped in" between the existing ones. When they both carry NPR news, the -2 is 7 seconds behind the -1. Some stations like WSJT 94.1 have the same programming on the -1 and the -2, with 7 seconds separation. WUSF has the analog fallback timing solved while the fallback on WSJT is a bit over a second out. end part 3 of 4 _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com