Strange hum on a HT1550

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w2sjw
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Strange hum on a HT1550

Post by w2sjw »

Guys,

OK, this is going to sound a little weird, but here goes:

I have a local PD here in NJ that uses a repeater on 155.565 with a PL of 107.2. The 1550 receives it just fine in 'normal' mode. When I turn on the MDC system for decode-only purposes, that channel develops a strange little hum only when the system is passing audio. My XTS5K does not display this behavior when configured the exact same way.

Are there any 1550 owners out here that are willing to do a 'control' test for me by setting their 1550's up the same as I have stated above, and then use another mobile/portable to test to see if their radio behaves the same way?

I honestly believe that it might be caused by something spurious from that PD's repeater, and not my 1550 (I just bought it brand-new from Jeff). If you guys would be as so kind to see how your units behave, I'd greatly appreciate it!
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Re: Strange hum on a HT1550

Post by W3MOT »

Sounds weird. I don't have a 1550, but I [did] own some 1250's and CDM's and I never experienced this problem. By any chance, what version software are you using? If I were you, I'd try make another personality (make sure it's a DEFAULT personality) and load it with the same information as the one with the hum with the exception of MDC Decode. When you hear them talk, switch channels to see if one has the hum, and the other one doesn't. Is there any way that we can hear what you're talking about? (IE post a MP3 file or .WAV file?)

Hope this helps alittle.
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Re: Strange hum on a HT1550

Post by akardam »

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Re: Strange hum on a HT1550

Post by W3MOT »

Good catch. Boy was I off! LOL :lol:
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Re: Strange hum on a HT1550

Post by w2sjw »

Thank you gentlemen for the quick replies! One last question I have if you don't mind - When sitting on a channel, the radio ends all transmissions silently (most all VHF users in this part of central NJ use reverse-burst). When I'm scanning, every transmission the radio stops on (regardless of channel) ends with a very rough burst of static. Is there a setting I might have missed?

I noticed a gentleman posting about the same issue here a while ago, but he did not say when he was getting that similar behavior.

Also - forgive me for being dense here, but were do I find that 'Global Tuner' option that was mentioned in the linked post? I'm looking all though the CPS to no avail...
Last edited by w2sjw on Wed Dec 24, 2008 4:57 pm, edited 1 time in total.
Scott, W2SJW
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Re: Strange hum on a HT1550

Post by W3MOT »

I have the same problem with my XTS's. What you're referring to is a Squelch Burst. It's annoying. Scanners do it all the time. Maybe akardam could help us out with this as well.
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Re: Strange hum on a HT1550

Post by N3IVK »

w2sjw "When I'm scanning, every transmission the radio stops on (regardless of channel) ends with a very rough burst of static. Is there a setting I might have missed?

Also - forgive me for being dense here, but were do I find that 'Global Tuner' option that was mentioned in the linked post? I'm looking all though the CPS to no avail..."



I noticed this too on many radios, spectras, CDM's, etc.

My thought is the priority sampling while your scanning. If you hearing a transmission, and the radio goes to sample the priority channel, it may miss the full reverse burst on another channel. Just my thought about it. Maybe try changing your priority sample time ? Maybe need to experiment to find a setting that works for you. I found setting scan up is quite a personal thing, everyone likes scan to work alittle different then the other. I personally like either 550 ms or 750 ms for priority sampling. But with that, I do have squelch tails...but willing to live with it.

The tuner is a separate program that is on the Pro Series RSS CD. I'd be careful to not stray off track with the tuner. Change only the settings you know and are comfortable with.

Happy Holidays !

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w2sjw
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Re: Strange hum on a HT1550

Post by w2sjw »

Matt,

I just checked my scan list configurations - I'm not running priority sampling (I've always hated that audio cut-out anyway).

I noticed that in the main radio configuration, under the 'Scan' tab, there is a setting for priority alert. I don't believe that has anything to do with this either, since I'm not using priority to begin with...
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w2sjw
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Re: Strange hum on a HT1550

Post by w2sjw »

Guys,

Well, hot damn, I figured it out! Since the issue with the raw squelch bursts only occurred during scan-mode operation, I decided to focus my attention there.

I found the settings for the scan lists to be where my answer was! On the 'General' tab, I set PL scan type to 'Priority & Non-Priority', and then unchecked 'PL Scan Lockout'

I went to the 'Advanced' tab & set the signaling type to 'Disabled'. It looks like I'm going to have to abandon the idea of doing MDC decoding with this radio. The 'And/Or' option set causes the radio to un-mute on MDC bursts from other co-channel users, even when they don't share the same TX PL (getting EMS from the Northampton County, PA opening up my county's EMS-1).

I'm assuming that if I set that feature to 'And', there would have to be both MDC & PL present to cause un-muting to occur, right? That's not going to work, because only 50%-60% of the users in my county have their MDC setup, and many use it on 'unkey'.

Somebody jump in here & tell me if I got that wrong... :lol:

EDIT - Well, I was wrong again. I set up a test between this 1550 and my XTS on an MURS channel, where I deliberately set the XTS to MDC with a different PL than the 1550 was set for. Nothing came over the 1550's speaker (only the LED flashed). When I set the XTS to the right PL, it opened the 1550's speaker (but it did not decode the burst's ID - maybe the radios were too close together, even on low power).
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Re: Strange hum on a HT1550

Post by laramiecountyCERT »

I have tried the Scan off and on with the same result. So I am at a loss as to what is causing this strange issue with mine as well. I have a VHF that does it but a UHF that does not so I will compare code plugs to see if I am missing something here and see what I can come up with.

Thanks for the reply and the work, hopefully we can find the problem and fix it between us.
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w2sjw
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Re: Strange hum on a HT1550

Post by w2sjw »

Well, mine is working as it should now. I told the MDC settings to require a proper matching PL/DPL for the data to pass, and then shut off signaling in my scan-list configuration.

The only outstanding issue I have is the hum that I mentioned in the first post, and when my buddy gets back in his office at the fire district next week, I'll have access to the tuner to change the PL baseband settings.

I tell you though, nothing I've learned about my XTS's in the last year prepared me for dealing with this 1550! :lol:
Scott, W2SJW
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