[ARDF] Fun and Frustration

[Dale Hunt WB6BYU]

Actually, Charles, we are already seeing steps in the direction of
software-defined receivers.  Both VK3YNG and DF1FO are using
microprocessors in their receivers, and the latter makes the
software available for modification.  Microprocessor control gives
a number of advantages, including:

(1) the ability to store frequencies, program a synthesizer, etc.

(2) the ability to provide timers

(3) the ability to tailor the gain response to give an accurate
indication of signal strength, to switch modes based on signal
strength, calculate approximate distance to the transmitter, etc.

(4) personal customization of equipment behavior to suite
special needs or favorite modes

(5) some amount of protection against someone reverse engineering
a copy  of the receiver and making them commercially (in that it
still would require them to write their own software to make it
functional.)

In either case, one can build the basic receiver bringing the
appropriate lines to the microcontroller, then have open source
code (and user options) to implement that part as each user
desired (including choice of processor, etc.)  One easy way
to do this would be to build the basic receiver on one board
with a connector to a separate processor board.  Then there
could be different board for those who want to use different
controller chips.

While perhaps not having the versatility of a complete SDR,
this uses existing circuitry and hardware without excessive
battery draw and weight (a potential shortcoming of computer
+ sound card implementations.)  At least it provides an interim
step to work on and optimize the RF circuitry while the full
SDR becomes more practical.


But if you do work on an SDR using existing technology, I'd
strongly recommend that you NOT use an iPhone if you plan
to use it in international competitions.  While we have been
rather lenient in Region 2 events, taking a cell phone (or any
other communications device) on a competition course would
be frowned upon at a World Championship.  (In some cases
I know the organizers have installed cell phone jammers at
the start and finish to prevent competitors in those areas from
talking to other competitors on the course.)  Stick with something
that is only designed for reception and/or playback.

Interesting ideas, though!


	- Dale WB6BYU


On 06 Oct 2009, at 10:05, Charles Scharlau wrote:

> One brief update on my comments:
>
> I'm seeing some strong evidence that it *might* be possible to  
> create a
> downloadable application that would turn an Apple iTouch into the  
> "computer"
> part of an SDR. So possibly taking an iTouch (or iPhone) loaded with  
> the
> right application, plugging an SDR front end into the microphone  
> port, and
> adding a directional antenna, you've got an all-mode ARDF receiver.
>
> Not to go off the deep end with futuristic ideas, but if this were
> implemented using an iPhone 3G (which includes a built-in digital  
> compass,
> lots of memory and the ability to display maps), you could have one  
> device
> that serves as receiver, map, and compass... not to mention music  
> player,
> web browser, cell phone, etc. etc. etc., with a Bluetooth interface  
> to use
> with your cordless headphones. The total cost could be well under  
> $100 for
> those who happen to already own the phone.
>
> Just thought I'd mention that in case it motivates anyone else to more
> closely examine the possibilities of an SDR ARDF receiver. Again,  
> please let
> me know if you might be interested in collaborating on an experimental
> design.
> OK, I'll stop my monologue now.
>
> -NZ0I
> On Sun, Oct 4, 2009 at 8:09 PM, Charles Scharlau <charles.scharlau at gmail.com
>> wrote:
>
>> In an earlier post I suggested that ARDF needed to evolve,  
>> including the
>> equipment we use. I hadn't commented with thoughts about equipment
>> evolution, but I thought I'd go ahead and post some thoughts...  
>> even if no
>> one asked :-) I think the subject fits the original subject because  
>> the
>> current situation with receivers contributes to the frustration of  
>> the sport
>> for both newcomers and those who have been playing the sport for  
>> years.
>>
>> I see three problems that need to be addressed: 1) availability -  
>> where to
>> find quality ARDF receivers in particular, 2) cost 3) complexity.  
>> Yes, I
>> know one can put out feelers and others will gladly identify someone,
>> somewhere who is selling a receiver. But that only serves to  
>> illustrate the
>> frustration of obtaining equipment: it is very much a treasure  
>> hunt, and a
>> buyer beware activity. When searching for a quality receiver one must
>> either buy a used receiver of uncertain condition, sans warranty,  
>> and sans
>> manual, or contact a foreign builder with uncertain product  
>> availability
>> (often uncertain product specs!), and all the problems that can go
>> along with communicating and remitting payment to an overseas  
>> entity. After
>> being in the sport for a while one tends to get numb to this  
>> situation, but
>> I'm always reminded when I must explain to a newbie the hoops that  
>> he/she
>> must jump through to purchase ARDF equipment.
>>
>> Loaner receivers are great, and shifts the issues of availability  
>> and cost
>> to the one doing the loaning, but it does nothing to reduce the  
>> complexity
>> of the sport... especially for the technology challenged.
>>
>> I believe that receiver evolution is needed sooner than later,  
>> especially
>> in countries where the sport has little or no history, and no  
>> domestic
>> receiver suppliers exist. But I think there might be the beginnings  
>> of a
>> solution to the receiver situation beginning to take shape: SDR or  
>> Software
>> Defined Radio.
>>
>> There is a cottage industry of SDR front ends. See
>> http://groups.yahoo.com/group/softrock40/ for links to information  
>> on how
>> the concept works and sources of kits. The remarkable things about  
>> the SDR
>> concept are the low parts count (ignoring the computer for now),  
>> the high
>> performance (including huge dynamic range, and high selectivity),  
>> and the
>> ability of the radio to gain new capabilities or
>> performance improvements with just a change to its software.
>>
>> Currently, the need to lug along a laptop makes an SDR totally  
>> impractical
>> as an ARDF receiver. One solution would be to substitute a handheld  
>> computer
>> instead of a laptop. But so far I've yet to identify a suitable  
>> handheld
>> with the requisite two-channel sound card. Another solution would  
>> be to
>> build a stand-alone SDR by interfacing the SDR front-end with a high
>> performance digital signal controller (i.e., an all-in-one DSP +
>> microcontroller IC). Such a stand-alone SDR holds the promise of an  
>> overall
>> parts count (and parts cost) well below any similarly capable  
>> receivers
>> available today. Also, with the appropriate software installed, it  
>> could
>> operate on any mode (AM, FM, CW, etc.), and possess features  
>> specifically
>> for the sport of ARDF (or for any other purpose that one can  
>> imagine). Come
>> up with your own whizzbang feature set for simplifying ARDF receiver
>> operation, or gaining an edge in ARDF competition, and most likely  
>> it can be
>> supported in the same SDR hardware in combination with the right  
>> software.
>>
>> I believe that a publicly-available hardware design using standard  
>> parts,
>> and an open source software effort, could eventually resolve all  
>> three of
>> the ARDF equipment issues I've listed - in the USA and elsewhere.
>>
>> Others more knowledgable than myself have probably considered the SDR
>> possibilities. I would be interested to hear/read your thoughts and  
>> ideas. I
>> would be especially interested to hear from anyone with DSP or  
>> hardware
>> design experience who might be interested in collaborating on an
>> experimental design. Feel free to contact me offline if your post  
>> doesn't
>> seem of general interest: charles.scharlau at gmail.com.
>>
>> 73,
>> NZ0I
>>
>>
>>
>>
>>
>>
>>
>>
>>
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