Astro Spectra Plus Audio

[4n6inv]

I've had a single high power AS+ W3 with a single 1/4 wave antenna that I've been using for over a year with little to no issues. I decided to add a high power UHF AS+ W3 last night. The audio previously has been top notch. When I finished this morning; I removed the old Motorola cellular type rectangle box speaker that I'd been using and replaced it with two very nice speakers from a flat screen TV (8 Ohm) that had produced terrific quality sound before I killed the TV. I figured that audio would be fantastic. I've never heard anything worse in my life. The volume was low, and when raised to the max, sounded worse than a 1960's era AM transistor radio - only louder.

I quickly replaced them with a nice set of Pyle 4 ohm speakers and the results were the same or worse. Both radios, harnesses, etc. are exactly the same. The only difference is that I'm using a Comet antenna combiner rated at 500 watts per radio, and a Diamond dual band antenna that I'd used before I installed the second radio. Range certainly isn't an issue because I'm hearing armature stations from 55+ miles away easily - just horrible audio. All of the local PD traffic is coming through, but the audio is horrible. What have I done??? I've always used Motorola speakers, but space is a big issue here.

I haven't changed any of the audio settings in the VHF, so that couldn't be an issue.

Any thoughts?

Thanks!

 

[4n6inv]

OK, I feel like a fool - but never heard of this one before....

It was the antenna. A dual band (oldie) based loaded Diamond Antenna. My dumb ass replaced the coax feed line and NMO mount twice!. Each time I measured infinity ohms between center and ground. When I attached the antenna; I was reading anywhere between 11 and 58 mega ohms. Seemed odd to me, but I thought - "That's a hell of a lot of resistance!" Couldn't be that. Guess what. It was. I replaced one of the Pyle speakers with and NOS Motorola and laid it on my seat. I replaced the Diamond antenna with one of the ridged Motorola 1/4 waves that the feds use - which it what I've always used. No sooner than I'd left my office, both radios were cackling like hens. Full, clear audio on both. Just damn. Live and learn...

 

[motorola_otaku]

I would lean more towards the Motorola speaker resolving the audio issue than the antenna... not that your antenna didn't need replacing anyway from the sound of it.

Communication speakers being "cheap" and having limited dynamic range actually works to your advantage in a mobile environment. The expanded low range of home entertainment/car audio speakers will add bass to the receive audio and make it sound muddy.


edit: If you're willing to entertain using non-Motorola speakers, go with a Kenwood KES-5. 40W at 4 ohms, better than anything Motorola ever made. I use one with the Fleet Radio speaker combiner in my mobile install.

 

[4n6inv]

OK; I'm going to do something that I hate to do; re-post on a subject I thought I'd already cured.

Although the audio is MUCH better with the other antenna (still scratching my head on that one), the audio is still tinny and nearly s bad as the old VSLOP. I can't imagine how a questionable antenna could have done any damage to my audio section(s). Both are "A" Rev vocons with DES-XL, DES-OFB, and AES encryption modules. Both have the latest firmware for both the vocons and the UCM's (Thanks for the firmware files!). The VHF was walking tall and working excellent before I swapped drawers to test the UHF that I built - and, yes; I did swap antennas to test the UHF with the Diamond dual band. It sounded great like that. It sounded as good as the VHF. Both had been tweaked to Mars recommended audio settings and were top notch. I've now tried both a Larsen and a Comet "duplexer" that combines the two different frequency radios into a common, low profile antenna. The Larsen was rated at 200 watts p-p. The Comet is rated at 500 watts p-p. Distance of reception is absolutely no issue. I was able to hear a skip from well over 200 miles away early this morning on the VHF.

In testing the output power; I have the VHF tuned to 105 watts out and reading 105 watts into the duplexer. Same with the UHF. I'm reading a little less than 104 watts out of the duplexer on both radios. No measurable SWR on the VHF. About 1.3:1 on the UHF - for obvious reasons - wrong band antenna, but still not bad. No significant heat appreciated, no excessive current draw. Both pulling around 0.443 - 0.448 amps in standby. 0.008 Off. Roughly 23-26 amps on transmit.

I've tried two different types of Motorola NMO antenna mounts and subbed the RG-58u coax with RG-400/u Mil-Spec coax. One was the traditional 3/4" roof mount NMO. The other was the thick penetration NMO mounts that's about 3/8" in diameter, but uses an adjustable "claw" on the shaft to compensate for different thickness penetrations and has a much more rigid top piece that screws onto the center. Both new in the wrapper Larsen mounts. The antenna (common) connector is a silver Amphenol PL-259 - soldered center, as wells as the side braid. No measurable resistance between the center conductor and outer shield. Both the inner and outer conductors measure less than 0.3 ohms, end to end. Excellent chassis ground. Still nothing measured with the 1/4 wave antenna attached. The "pigtails" from the duplexer are both RG-400/u with silver, Amphenol PL-259 connectors to silver, Amphenol BNC connectors attached to the radios - also with silver Amphenol BNC connectors. Both pigtails are equal lengths (30"). None are anywhere near any "noise source.

Just for snakes and gerbils; I'm going to re-read the audio settings during lunch, but am not expecting a smoking gun there. I'm at a loss. I've used both duplexers previously with a Kenwood multi-bander ham with no issues, but never with a Motorola.

Anyone with any experience, suggestions - ANYTHING? I'm stumped. Although the speakers are slightly smaller (~3.5" in diameter); both are much higher quality with the current Pyle's rated in excess of 100 watts. Too little power? Just don't know. Oh, yeah; both had been recapped with Kemet T495 series tantalum caps - except for the obvious 200uF's in the HP PA, which were were replaced with Rubycon's. Both either came equipped or were retrofitted with front end preamps that worked fantastic. I live in hell, so intermod is NOT an issue here! Distance is.

Thanks for any morsel of advice.

 

[4n6inv]

I would lean more towards the Motorola speaker resolving the audio issue than the antenna... not that your antenna didn't need replacing anyway from the sound of it.

Communication speakers being "cheap" and having limited dynamic range actually works to your advantage in a mobile environment. The expanded low range of home entertainment/car audio speakers will add bass to the receive audio and make it sound muddy.


edit: If you're willing to entertain using non-Motorola speakers, go with a Kenwood KES-5. 40W at 4 ohms, better than anything Motorola ever made. I use one with the Fleet Radio speaker combiner in my mobile install.

First and foremost; I couldn't find the "Thanks" button. But, thank you very much. I know that you are particularly knowledgeable about the AS+s', as is Mars. So, your advise is always appreciated. Thanks!

Deal is; with these "high end" speakers, the audio is extremely tinny; with NO bass whatsoever. Plus; when I only had the single drawer and swapped the V for the U; both sounded magnificent. Just didn't get around to re-wiring and installing them (with a shoe horn) Sunday night. What you said makes perfect sense, though. I'm going to pull a couple of NOS full sized dash / console mount Motorola speakers when I go home for lunch and plug them in. Operationally; both radios are ship - shape. But, the audio would be a deal breaker. Yeah; I know: It's way better than when I started this rant yesterday, but I'd be screaming and pulling my hair out after more than 10 minutes of rx'd audio. Completely baffled. I mounted both radios on opposite ends in the hatchback of my poor old Chevy Blazer with both W3 wiring harnesses run under the driver's and passenger's side, respectively. I was concerned about that switching diode in the PA that sometimes gets blown when RF sources are too close. Sure is no deal in receiving! The only difference - and I know that it's a non-issue, is that I have a 1439 siren / PA attached to the VHF for my public safety work. It's mounted between both radio drawers with room to spare and has it's own power supply from the battery.

Thanks, again for your valuable input. I'll hit the "Thanks" when it appears! I'll keep you posted. Bears watching for certain.

 

[com501]

I would look at two things.

The actual impedance of your high end speakers versus the factory speakers and are they the SAME, and are your after-market speakers multi-cone types wth perhaps a built-in crossover that is messing with your speaker grounding, or did your after-market speakers add a ground point to the audio stage which the AS+'s will not like?

 

[4n6inv]

I would look at two things.

The actual impedance of your high end speakers versus the factory speakers and are they the SAME, and are your after-market speakers multi-cone types wth perhaps a built-in crossover that is messing with your speaker grounding, or did your after-market speakers add a ground point to the audio stage which the AS+'s will not like?

Very, Very good point! Actually; yes, I did test the impedances of the speakers yesterday. The Motorola cellular type measures 5.5 ohms. The Pyle (Dual Cone, BTW) dead on 4 ohms, and yes polarized - although I was careful to observe that during the installation. Good point about the crossover because it sounds like only the tweeter cone is activating.

As far as the ones from my Sharp TV; they are single cone, but damn nice speakers. 8 ohms measured and rated. Sounded fantastic inside the TV before I murdered it with my DVD Jukebox. They are slim, low profile, single cone speakers that sound the worst! They have multiple baffles, and I suppose that that could contribute to the acoustic principals that may have been implemented with the case design of the front panel of the TV set. They were the first ones that I tried because they are slim, low profile. But, I unplugged them before I blew my brains out. I tried the Pyle's yesterday at lunch. Very little improvement. Just damn. Long rant in my post.

Fast forward to the shenanigans last night that I thought had brought everything back to an acceptable level. I was so tired and hot that I didn't really give them the acid test last night. Chemo is a bitch!

OK; to sum this all up; I've opened ANOTHER can of worms: I went home at lunch and replaced the Pyle's with NOS Motorola speakers. Problem pretty much solved. Again; too hot to do an acid test and not enough time today. But; excellent suggestion, and HUGE improvement. Question is: Where in the hell am I going to put them?

Biggest earth shaker that I noticed was: When I keyed the mic at full power on any frequency, the LCD display began throwing random pixels everywhere and started to dim (the contrast - NOT the back lighting). Just damn. My only explanation for that is chassis ground. When I was disassembling everything Sunday night; I noticed that my chassis ground(s) were somewhat loose in the door wiring trac, and that there was significant oxidation on the underside of the self tapping screw that penetrated under my car. No big shock there. So; I removed it, shortened it, and bolted it to one of the rear seat chassis mounting bolts. Damn, that ought to make a good ground.
But, not a lot of bare metal. Plenty of conductance, but, at the cost of how much noise and power loss in completing the ground? How much actual surface contact? Maybe just enough to power them up and work, but not giving them the proper BSOP. Unfortunately; I'll have to un bolt the rear seats - and I'm still aching from that Sunday night - and actually drill another through the uni-body chassis and grind away the paint on the interior to insure proper grounding. Pretty important with that much amperage! Your thoughts?

I know a lot of you have done installs - especially Jason - Do you, or would you even consider making your ground with a huge anodized bolt welded to the chassis of the vehicle, but with a nice, huge, zinc hardened bolt holding it in place? Have I opened a can of worms in doing so? I know BSOP is to drill through the chassis, grind away the surrounding paint and use copious washers to ensure a good contact. I was just too lazy (at 01:00 Monday morning!) - had plenty of supplies, but figured - "How much better ground can I get than torqueing this thing down with the strength of a gorilla onto a metal surface?

Please don't laugh (in my face, at least) if this is the case. Please just politely say: "Hey; I wouldn't do it that way, Dude." I love my radios and am grateful that I have two really nice ones in my POV after 50+ years of tinkering with them. They'll likely be the last radios of any significance that I own. I want to enjoy them.

Thank you all for your valuable, common sense input. It's given me much to consider to remedy this.

 

[4n6inv]

Resolution

Resolution. I think. I reinstalled and repositioned the old cellular speaker that I'd used before. Works and sounds great. Less filling. Had another - just like it- spliced the connectors and attached to UHF AS+. Ditto. Came in at 0300 this morning and pulled my car in. Where to mount the speakers? I tried a few combinations, and this was the best I could do. Road test. Flawless. Mars audio settings were still in tact , and still sound great. Time will tell. Lookin' good at this point.

Not being one to leave well enough alone; I decided to give the Diamond dual band antenna another try. Last on the agenda, and only a brief road test, but even it's working OK. I haven't put the watt meter on it to compare, but that will happen this evening. That's still a little freaky about the 11 - 58 mega ohms between center and ground. The power test will be brief; rest assured. Only thing I can think of would be some cross-over caps in the base load. Sort of passes the sanity test since the resistance isn't constant, and the very low voltage of the ohm meter could cause the cap values to change when applying power. Dunno... Could be breakdown over the antenna being 15 years old. Physically sturdy, but I've seen that before. Another "Bears watching".

Regardless; I am going to redo the ground straps. Since I'd already trimmed them back; I'm just going to cut a ~3" hole in the carpet under the seat, Dremel a 3/4" area of paint to bare metal. This after locating one of the frame rails, drilling a hole through the floor pan and into the frame rail. I'll tap it with a #10, or 1/4" bolt and do a proper ground. At least I know that will eliminates a few of the "what if's".

In summary regarding the audio; I'm going to agree with com501 about the Pyle speakers - although I never saw any crossover circuitry. They were tinny duds. The 8 ohm TV speakers - dunno... I'm inclined to believe that there was a special acoustic engineering situation going on. No longer have the face of the TV that I cannibalized, so I can't say for sure, but they sound like crap on pretty much anything. So; the Monkeyrolla speakers - cellular and LMR are both 5.5 ohms. The Pyle's were the closest at 4 ohms, but again; I'm going with com501 and his theory. Makes total sense. The Sharp TV speakers - I think - are just pig ears turned into silk purses. 8 ohms. I expected them to be softer, but I didn't expect the to sound THAT crappy! Nonetheless; problem solved.

Attached are a few early morning photos. Still need to figure where to hang the second mic that's airbag friendly. Sorry for the crappy cell phone photos - hindered even more by the early morning light shining right on them.







Thanks for all of the help / suggestions / comments!

 

[motorola_otaku]

Sorry I'm a little late replying. Good to hear you've mostly got the receive audio issue straightened out. As far as mobile communications speakers go you really can't reinvent the wheel - a Motorola or Kenwood speaker is the best you can get. One thing I have done in the past that will give you a little extra bass without muddying the audio is to gut an old Saber SVA amplified speaker (the kind with the large metal housing) and use that straight to the radio. IIRC the stock speaker cone is 3.2 ohms/12W so you're good to go for any Astro radio. They sound particularly excellent on lowband equipment, especially Syntor X9000s - really gives it that 70s vintage lowband sound. And don't forget you've got treble settings you can fiddle with under Radio Wide - RX Audio Control.

As far as high-current DC grounds go, what I like to do is find the factory battery-to-chassis ground, beef it up with 2 ga. or 2|0 welding cable and crimped/soldered copper lugs, and then run that back to the radio location from the chassis bolt. That way you know the battery chassis ground will never fail, and if it does it won't pull current across your radios.

 

[4n6inv]

Thanks for the input. I adjusted the audio gain and treble controls until it sounds like a Yamaha concert amp. The audio is wonderful with those two little old cellular (actual Motorola) speakers.

What really blows my mind is that I had a longer than usual drive yesterday and with that old Diamond dual band was able to hear VHF freqs better than with one of the high-grunt Motorola 1/4 Fed antennas. And, that's running through a combiner. No probs on VHF. There are few and far between UHF pairs out here, but I don't seem to have the "distance" that I have with VHF - even considering what I'm working with. I'm going to fiddle with the preamp mod that I did on the front end of the UHF, but it tested a .2 receive on the bench. I fried a diode on one that I did a while back - working on the ceramic substrate, with similar symptoms. Could be the issue here. Bears watching.

I wish I had room for a full sized speaker, but I just don't. These sound great with a little tweaking. Digital or analog. And I agree 100% about the old amplified Saber CC speakers. Used one of those on a rapid deployment console that I built a while back and it was awesome! It was attached to an XTL5000 800MHz in a Halliburton case.

Thanks again!

 

[4n6inv]

OK. Issue(s) resolved. Audio is tree top tall. RX and TX, ditto. Still using the Diamond dual band antenna - which outperforms ANY single band, or multiband antenna, and has the power capability to handle the situation. It's even 8" shorter and less conspicuous than any other antenna. It's about 13-14" tall and has ACTUAL gain on both bands. It's phenomenal. Of course; I live in hell; with nothing to interfere, but it's range is outstanding - even at the 15 year mark. No measurable SWR on either band. 105 out of both units. Less than 1 watt reflected. Receiving Public Safety stations 120 +/- miles away clear as a bell and consistently. 440 pairs; well, pretty good, but hey; we're dealing with other hamsters. Still damn good to hit and rx stations 55+ miles away (one, actually close to 100 miles away) with no effort. I removed the rear seats and did a proper ground with a 1/4" stainless bolt threaded into the chassis. I replaced the diode and transistor on the UHF preamp, and that seems to have eliminated any other issues.

If there's any interest, here are a few shots of the final setup. I thought I did pretty good with the W3's and not interfering with the airbags. No; I don't mean me. Still an airbag.

Any additional thoughts, suggestions? Happy camper.