[OZAPRS] FM828

[Ray Wells]

You beat me to it Geoff.

The FM828 may be 30 years old but nothing can touch it for reliability 
and, performance at high density RF sites. The rx sensitivity of 0.25uV 
is not to be sneezed at.

The measure of a receiver's sensitivity isn't what the signal generator 
on the bench says. The real test is to feed the sig gen into an 
attenuator Tee. Start with a 50ohm termination instead of an antenna. 
Obtain a sensitivity figure (which won't be what you get feeding the rx 
directly). Next, replace the dummy load with the real world antenna and 
re-check sensitivity. Chances are the rx will need lots more RF if the 
rx is of the broadband front end variety and heaps more if it's a 
typical AR rig. The FM828 will hardly blink, if at all.

$60 for a pair of commercial spec rocks makes for a good, economical, 
reliable, single channel rig for elevated sites.

I had two FM828's in BBS service here for 10 years and another on 
440.050 for 12 years. Plenty of RF here and they didn't have to be 
touched. My local aprs digi is an 828 and gives the same reliability.

Ray,
vk2tv

On 24/02/11 18:10, Geoff Gatward wrote:
> We've had an FM-828 running VK2US-1 in the heart of Sydney for about the
> last 10 years, and it's been at least 7 years since anyone has touched
> it.  Not bad, as about 100m away is the highest concentration of RF crud
> in sydney up on the GPT and AAPT buildings.  This digi works very well,
> well over 100km away - and all without any external filtering.
>
> We did have a commercial rig up there, and also an FM-900, however the
> noise floor and intermods rendered them useless in the high RF
> environment.
>
> Many (if not all) digipeaters around southern VK2 are running an 828.
>
> True there are some 'dud' units out there, but for a single purpose,
> fixed frequency application the humble FM-828 (and it's base cousin the
> FM-814) are bullet-proof.
>
> The new digi going in here in Alice is probably going to be an FM-814
> once it is recovered from the voice repeater upgrade...
>
> Geoff
> VK8GG/VK2XJG
>
>
>
> On Thu, 2011-02-24 at 07:40 +1000, Howard Small wrote:
>> The Tablelands Amateur Radio Club has agreed to put up a digipeater to
>> link to ours in Cairns (VK4RIK-3) and is offering an FM828 for the job.
>> One of our members will supply a TNC but before they get crystals for
>> the FM828 we need to check if there are any issues.
>>
>> Has anyone used an FM828 for a digi? If so, can you please give me
>> details on the interface to the TNC and any other info that may be useful?
>>
>> Thanks,
>>
>> Howard
>> VK4BS
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