ARD25 digital decoder disappointing

[Mike_Alpha]

I just received my ARD25 Apco25 decoder and I'm very disappointed with it's performance with the AOR AR8600. I've done the all mode IF mod and although the AR8600 does scan, the width of the 10.7MHz IF output is just too wide to be used on frequencies with 12.5KHz spacing.

The ARD25 cannot filter out the adjacent signals to the frequency being monitored and the slightest bit of interference disrupts the digital decoding. Also, while the AR8600 is scanning or searching, a sound similar to a horse galloping comes out of the speaker. It also stops on any interference signals caused by adjacent channel activity up to 50Khz away.

The audio from any analogue transmissions that go through the ARD25 are distorted with bad clipping. I'm thinking that the IF output level could be too high and overloading the front end of the ARD25. But you'd think AOR would have matched the signal level between the units. I might try an attenuator in line and see if that helps.

I read somewhere that the SCAN-L guys have got the ARD25 to work with other scanners using a 10.7Mhz IF. They also said they have got the decoder working with a discriminator output signal. I have not found any information on the net regarding how the discrimintor signal is input to the ARD25.

If anyone has any suggestions or links to the discriminator input modification, please post here.

Mike

 

[KC1UA]

Mike,

I have an ARD25 that I use with an AOR AR-5000 and I'm not having any of the difficulties you list. From the sounds of your post it seems that you may be running your 8600 in WFM. If the all mode IF mod has been completed that should not be necessary. NFM should work fine.

The ARD25 works "ok" as far as I'm concerned. I purchased it as an accessory for my 5000 with DX'ing APCO-25 signals in mind. It has done that for me, but I must admit that it does not provide the constant quality of audio I get from my PRO-96 or my BC796D. It's very fussy with certain signals. Passing the audio through from the external speaker jack to use it with analog signals is not even a viable option, it sounds awful. What I've done as a workaround is simple. The 10.7 IF is the only connection from the 5000 to the ARD25. I turn the 25 on and turn its volume off. If I come across an APCO-25 signal I turn the 5000's volume off and turn the 25's up. I've noticed that the 25 doesn't need much volume; with no AGC it blows you out of the room at anything past 9 O'Clock on most APCO-25 signals. I continue to listen to analog signals via the speaker I use with the 5000. Works fine that way, or as fine as it can. I'll play the guinea pig here and say that if I had it to do over, I likely would not purchase the ARD25 at the price it's at. If AOR lowered it by about $200 that might make a difference.

I have a friend who uses one with his Icom IC-R7000 receiver and is happy overall with its performance. I haven't heard anything more about its use with a discriminator output. Hopefully we will, as that would certainly greatly expand its use. As said before and time and time again, AOR would surely benefit by halfing the price. I just don't think they're going to sell many at the current price....ok, so I'm a sucker!!! :wink:

Sorry to hear you're having difficulties. I know the manual clearly says that WFM must be used for the 8600, but if you've done the IF mod that should not apply. This info came to me directly from AOR USA, as I owned an 8600 also (since sold) when I bought the 25.

Best of luck!

 

[Mike_Alpha]

Scott, The AR8600 IF mod has been done, so it is scanning OK. I have all the channels in the scan group programmed for NFM or SFM.

The WFM 10.7MHz output is causing the problem. Although the scanner stops on an active frequency, any adjacent transmissions received are not filtered adequately by the ARD25. The resulting interference and bleed through disrupt the digital decoding.

I'll try attenuating the IF output soon and report if that makes any difference.

Mike

 

[cbradar]

ARD25 vs Icom IC-R7000

I own an Icom IC-R7000 and it has a 10.7 Mhz IF Output, originally designed for use with a TV Adapter, which I have.

The R7000's BNC output of 10.7Mhz carries a DC voltage on the center wire to power the TV Adaptor, but the DC can be externally blocked by a small capacitior. What capacitor value would you suggest?

Has anyone tried using the ADR-25 on the R7000 reveiver? If so, what were your results?

I also have a Radio Shack PRO-2006 with both 455Khz and 10.7Mhz outputs. I would like to hear about any results with these radios hooked up to the ADR-25 as well.

I am thinking about buying the ADR-25, but won't until I hear from someone who has sucessfully used it on the R7000 and/or the PRO-2006.

Also, how well does the ADR-25 work on frequencies used on Military frequencies?

Are there any other manufacturers of such adapters that may work better than the ADR-25?

 

[KC1UA]

I just sold an R7000 with ARD25 decoder. Worked very nicely for me. I used an inline F connector type DC block, I think I got it from Radio Shack. Worked well and there was no degradation as a result. The ARD25 decoded well on weak signals that did not move the 7000's S meter. It was also interesting to use the ARD25 connected to Hyperterm in Windows and watch some of the information sent by it as it decoded.

I did not pass the analog audio through it, I just made the 10.7 IF connection. If I came across a P25 signal while searching I'd just turn down the 7000's volume and turn up the volume on the 25.

I can vouch for its performance on an AOR AR5000, an AOR AR5000A+3, and the R7000 of course.
It is an expensive item that has never really become mainstream but I wanted a decoder on a communcations receiver. This worked well for me.