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Message |
    
Hyperno_1979
Member
Username: Hyperno_1979
Post Number: 91
Registered: 12-2005
| | Posted on Friday, July 28, 2006 - 8:16 pm: | 
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Can anyone explain the term "Dirty Radio" to me? Reason being, apparently someone has brought a few Delta Forces into Australia and quite a few people in Melbourne are up in arms over them. I heard on the local call channel people whingeing about bleeding over 3 channels either side of where these radios are being operated. You hear people saying " so and so has a delta force can't you pick the dirty radio?". This escalates into an all in brawl, quite entertaining. I have checked my 357 and it does bleed over only 1 channel to my mobile but i expect that as it puts out over 4 times the power of a Delta Force, but i get bleedover from truckies on channel 8 am while i am on 35 lsb. This is from only standard cb's not Magnums or Galaxy's etc. Could someone please clarify this for me.
Cheers and Beers,
Bob CEF 703. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1317
Registered: 6-2004
| | Posted on Saturday, July 29, 2006 - 1:35 am: |
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Dirty radios are simply radios that splatter onto other channels. It can be caused by poor design, modification (cutting the limiter), or just a bad adjustment of the limiter.
Splatter can actually be sidebands on adjacent frequencies caused by more than 100% modulation, or it can be pseudo-splatter that your receiver can't filter for one of two reasons:
1 - Strong signal overload. You can generally tell if it's strong signal overload by turning back the RF gain a great deal. If the splatter goes away, it was just your receiver unable to deal with the strong signal by cutting back it's gain. Of course if the receiver has a poor design it might still have a problem.
2 - Lack of selectivity. Your receiver might not be overloaded, but the filtering can't eliminate the adjacent signal because it's not selective enough. Usually it will only happen on the frequencies adjacent to yours.
Channel Guard Filters can REALLY help with the second, but probably won't help with the first because the components effected are earlier in the receiver chain. |
Hyperno_1979
Member
Username: Hyperno_1979
Post Number: 94
Registered: 12-2005
| | Posted on Saturday, July 29, 2006 - 8:50 am: |
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Thanx Hollowpoint,
As i said, i get bleedover from truckies 20 odd channels away, not only on my 357 but on my cb's as well as my FT7. A major highway is only about a 1/2 mile away. Doesn't happen all the time though. But it seems to me that those in Melbourne are blowing gaskets just because there are Delta Forces in town. I am only going on what i hear when skip is running from Victoria. All whingeing about these radios. Reminds me of a time when 2950's were all the rage.....those that didn't have them were probably jealous. But that's what i couldn't understand Hollowpoint....my 357 only splatters 1 channel to my mobile, an AX144, in the same street, these guys are saying that a Delta Force is splattering 3 channels across a whole suburb. I don't know where they originally came from or what but it has caused a bit of a stir......lol. Bit of a giggle to listen to.
Bob CEF 703. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1318
Registered: 6-2004
| | Posted on Saturday, July 29, 2006 - 10:25 am: |
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I'm guessing that the problem you have locally is because of amplifier harmonics. Two reasons for that guess - you're using an HF rig which usually have pretty good front ends, and it doesn't happen all the time. If it happened all the time I'd say that the FT7 needs an alignment and/or a narrower SSB filter.
The Melbourne folks sound biased against that radio for one reason or another. Probably because some local has one that's hacked and really splatters. It's easy to splatter a few channels with a dual final radio if it's been hacked badly.
Your 357 is apparently pretty clean because you only get adjacent channel interference with it locally. I wonder how the FT7 reacts to it? I find my TS450 nearly immune to adjacent channel interference as long as the radio isn't overmodulating.
What is it with the AX144 down under? I've read more than a few glowing reports on the internet about those radios from Aussies who love them. They're basically ignored here in the USA in favor of the 148/Grant. While I agree that the 148/Grant is a better radio, the AX144/146/PC122 series of Uniden radios are great SSB rigs. I wish the 148/Grant had the LED indicator for mode that the AX144 does. It's a nice touch. |
Tech237
Moderator
Username: Tech237
Post Number: 468
Registered: 4-2004
| | Posted on Saturday, July 29, 2006 - 11:26 am: |
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Ax-144 now that was a nice radio. Almost asa good as the old President Mckinley and Super panthers i used to own. |
Hyperno_1979
Intermediate Member
Username: Hyperno_1979
Post Number: 100
Registered: 12-2005
| | Posted on Saturday, July 29, 2006 - 4:43 pm: |
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I think the AX 144 is or was so popular was that it does the job and does it well and also the size difference to the Grant. The Grant was a big radio and in most instances was too big to put in the average motor car. The Grant was more suited to base application but then those who wanted to stick with Uniden went to the Washingtub. As for my FT7 i've had it for about 15-20 years and more than likely is up for an alignment, but same old story, finding someone over here that still works on them. I rang around umpteen places looking for a tech for my TS820 and one place that has been in business since Jesus played fullback for Jerusalem had the audacity to ask "Whats a TS820?" Ya gotta love that! One place thought that the only HF radios in use today were for the RFDS. "We just send them off to Codan". Anyway enough of my rambling ....i've gone right off the subject here but thanks Hollowpoint and Simon for your input, it has been invaluable.
Bob CEF 703. |
Tech237
Moderator
Username: Tech237
Post Number: 471
Registered: 4-2004
| | Posted on Saturday, July 29, 2006 - 5:49 pm: |
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Bob,
Funny storythat kinda involves an FT-7 I used to own.
It was bolted in my 77 Celica Liftback (this 1986)and I was travelling regularly between Newcastle, Sydney and Bathurst. Because I had recently broken a windscreen I had placed the rego label on the rear passenger quarter window (as was allowed by law then).
The car was parked in Strathfield and I was in an office working. Came out at 5pm to find some one had broken the quarter window and removed the AM CB but left the FT-7.
Oh yes I got stopped on the way back to Newcastle by a policeman who was going to book me for no rego label. I just quietly handed him the bag of broekn glass on some of which you could see the remains of the label, and told him it was a jig-saw puzzle and if he wanted to read it HE had to put it together. He let me go with a warning to get a replacement the following morning. |
