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HD DX

W

w9wi

I now have my second HD DX logging...

About a week ago, shortly after sunrise Eastern time I noted WOWO-1190 with a pretty blazingly strong signal and, since it *was* after sunrise, their IBOC was on. Left the receiver on for awhile and eventually noted "WOWO" in the display. 330-mile digital DX.

Tonight, reports on the National Radio Club mailing list suggested WOAI-1200's IBOC was on. The radio's HD light was blinking (indicating a HD signal was present) but with WOWO awfully strong I never figured anything would come of it. On the Receptor HD it's pretty common for a distant IBOC station to cause the HD light to blink. It takes a FAR cleaner signal to deliver any digital audio. Left the radio on 1200 anyway, with the analog WOAI audio sounding pretty good.

Checked back around 0130 CDT - and noted "WOAI" on the display. 800 miles or so, not bad!

Again, this is only a "text ID", no IBOC digital audio was received. So far my distance record for IBOC digital audio on AM remains about 18 miles<grin>. <WLAC>
Radio is Boston Acoustics Receptor HD; antenna 260-foot center-fed wire. (AKA 160-meter dipole)
 
>
> Again, this is only a "text ID", no IBOC digital audio was
> received. So far my distance record for IBOC digital audio
> on AM remains about 18 miles.
> Radio is Boston Acoustics Receptor HD; antenna 260-foot
> center-fed wire. (AKA 160-meter dipole)
>


Interesting results. As to the 18 mile HD results, when talking groundwave might the limited success be due to cross polorization issues? If memeory serves there's a 20 DB loss when going from vertical to horizontal (and of course visa versa). I have the B.A. and use a Radio Shack passive loop for Am and have no trouble receiving HD signals from my local market, NYC (transmitters in Jersey about 25 to 30 miles from me or so). WBZ, Boston causes the HD light to flash as do a number of other out of market stations running the IBOC exciter. An inverted vee might prove a more efficient antenna in this case. How do you like the selectivity on this radio? Mine is spectacular. I've rceeived WLW during critical hours while WOR is running it's exciter. That's a first adjacent signal. ON FM I use rabbit ears and have no problems with any of the NY IBOC stations. One issue I believe exists is that the sensitivity of each radio might be an issue. I know people with the radio who have marginal reception while mine has no trouble. I had to return my first one because it was deaf.Well, it's a first generation radio so some issues still remain but it's a great radio if you have the right antenna and are willing to take some time to learn a bit about what the radio can and can't do. Hey, it's a table radio, not a communications receiver.
 
> Interesting results. As to the 18 mile HD results, when
> talking groundwave might the limited success be due to cross
> polorization issues?

Well, it's mostly because the 18-mile station (WLAC) is the *only* HD AM station within about 130 miles. The next nearest is WHAS but 130 miles over our poor ground conductivity is too far for HD reception. The HD indicator does blink (and I'll bet if I left the radio on 840 long enough I'd get a "text ID") but so far no audio.

I also get the blinking HD light frequently around sunrise and sunset on various other stations - WLW, WCKY, WRLL, WGN, WSCR, and WBBM, probably others. So far no audio from anyone except WLAC and no text from anyone except WLAC, WOWO, and WOAI.

I have tried the loop that comes with the radio (not the internal one inside the case, but the external one that's like those that come with stereo receivers). It's considerably worse. As in, I was able to get WLAC to lock in with audio for a few seconds. (with the 160m dipole WLAC-HD locks in for audio about 95-99% of the time)

> efficient antenna in this case. How do you like the
> selectivity on this radio? Mine is spectacular.

Absolutely. Both on AM and FM. On AM the set seems to have some kind of cancellation circuitry, WLAC's HD sidebands don't cause nearly as much interference to the 1490/1500/1520/1530 adjacents as they do on even the best analog radio. On FM this thing is on a par with my Technics ST-G50 tuner - which has been modified with 110KHz IF filters.

FM analog sensitivity is pretty good too. (and it has RDS for analog stations) It's reasonably "crunchproof": I have yet to hear any spurious responses despite connecting a 9-element Yagi antenna. I do live over 15 miles from the nearest FM station.

On AM it seems to like to go into some kind of oscillation when a large antenna is attached. It also overloads pretty badly during the day on the 160m dipole. (strange, as the nearest AM station is 10 miles away and only 500 watts) I'm sure BA never figured anyone would connect a 260-foot antenna to their radio!

I have to say, I am decidedly unimpressed by the digital sensitivity. I can have WLAC's analog signal at absolutely rock-crushing strength and not be able to get the digital to lock. Similarly on FM, with the wire antenna that came with the radio the analog signals of our three FM HD stations are absolutely full quieting but none of them will lock in HD. I have to connect the TV antenna to get FM HD.

(I'm hearing BA is now providing a "T" antenna for FM, which will probably work a lot better. I don't have anything between the wire and the TV antenna.)

But my point is that HD, both on AM and FM, seems to require much more signal than is necessary for analog.
 
BA radio AM antenna jack input impedance? (Re: HD DX)

Hello Bob,

What kind of AM antenna jack (or terminals) does the BA receiver have, and what is its rated input impedance?

Using it with your 160 meter dipole, you could put an attenuator between the feedline and the radio to prevent overloading the front end when listening to local AM HD stations.

Also, I found an interesting indoor 160 meter attic antenna that should work just as well for HD AM reception: http://www.qsl.net/g3pto/roofant.html

This antenna is a folded vertical with a top-mounted loading coil and a wire "fan" top-loading capacitance hat connected to the *lower* end of the loading coil. Since the antenna is folded, the loading coil is actually at a low height and is easy to gain access to for fine-tuning.

Using the designer's "standard" three 8' - 12' top-loading wires, it would be interesting to see what top loading coil values (certainly less than needed for a base loading coil) would resonate the antenna at various AM frequencies for given lengths. -- Jason
 
Re: BA radio AM antenna jack input impedance? (Re: HD DX)

> What kind of AM antenna jack (or terminals) does the BA
> receiver have, and what is its rated input impedance?

Push terminals, similar to what's used for speakers on stereo receivers. As for the impedance, I have no idea. I'd guess a few hundred to a few thousand ohms.

> Using it with your 160 meter dipole, you could put an
> attenuator between the feedline and the radio to prevent
> overloading the front end when listening to local AM HD
> stations.

I probably should. What I generally do when listening to the local station is select a different antenna - I have six on the same remote switch, and the rest are less efficient (to varying degrees) on the BCB.

> Using the designer's "standard" three 8' - 12' top-loading
> wires, it would be interesting to see what top loading coil
> values (certainly less than needed for a base loading coil)
> would resonate the antenna at various AM frequencies for
> given lengths. -- Jason

I don't think resonance is important for this application. That's more a concept for when you're transmitting, when a mismatch can result in physical damage due to excessive voltages/currents. In a receive-only application on the AM band where feedline losses are negligible, it's more important to get more signal into the receiver -- and in the modern AM band, probably more important to knock down noise and interference than to get more signal.

What I really should have is a large open-frame loop. (maybe 2-3 feet or so) The nulls can be pretty tight.
 
Re: BA radio AM antenna jack input impedance? (Re: HD DX)

Living in the NY suburbs I have to admit that my reception issues are different than your's are. Here it isn't for lack of RF. We live in an RF jungle. I found the reception with the supplied loop and wire marginal at best. the passive loop for Am and the Rabbit ears (horizontally mounted)provide more than enough RF to the radio to receive all the local HD stations. Again, at least in this part of the country people don't have to search for stations more than 30 miles away. Our broadcast bands are filled to the brim.
 
Re: BA radio AM antenna jack input impedance? (Re: HD DX)

> Push terminals, similar to what's used for speakers on
> stereo receivers. As for the impedance, I have no idea.
> I'd guess a few hundred to a few thousand ohms.

I just e-mailed Boston Acoustics to ask them. Even though I don't own one I'm curious, and I'll post their reply here.

> > Using it with your 160 meter dipole, you could put an
> > attenuator between the feedline and the radio to prevent
> > overloading the front end when listening to local AM HD
> > stations.
>
> I probably should. What I generally do when listening to
> the local station is select a different antenna - I have six
> on the same remote switch, and the rest are less efficient
> (to varying degrees) on the BCB.

Michael Toia K3MT's on-ground "Grasswire" antenna http://users.erols.com/k3mt/graswire/graswire.htm works well for AM reception too, as it is sensitive to vertically-polarized radiation off its far end (you point the far end at the desired station).

> I don't think resonance is important for this application.
> That's more a concept for when you're transmitting, when a
> mismatch can result in physical damage due to excessive
> voltages/currents. In a receive-only application on the AM
> band where feedline losses are negligible, it's more
> important to get more signal into the receiver -- and in the
> modern AM band, probably more important to knock down noise
> and interference than to get more signal.

You're right--being an occasional Part 15 AM broadcaster, I'm sometimes a bit "manic" about antenna matching. :)

> What I really should have is a large open-frame loop. (maybe
> 2-3 feet or so) The nulls can be pretty tight.

Yes, that old standby will pull 'em in (and effectively "filter out" the stations you don't want). -- Jason
 
Re: BA radio AM antenna jack input impedance? (Re: HD DX)

> Michael Toia K3MT's on-ground "Grasswire" antenna
> http://users.erols.com/k3mt/graswire/graswire.htm works well
> for AM reception too, as it is sensitive to
> vertically-polarized radiation off its far end (you point
> the far end at the desired station).

I've done something similar with considerable success. About 400' of electric-fence wire on 2' sticks run in a straight line. 9:1 balun at the feed end, terminating resistor (theoretically 450 ohms but 470 is close enough) at the far end.

Usually pull it up this time of year, makes it too hard to mow<grin>.
 
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