[ARC5] Amazon Sig Gen as Crystal Subber

[Tim]

Hi Ian - The link Mike sent is good regarding user questions/answers.
There are other reviews on YouTube / Web.  There is another "version" under
a different company name that is packaged in a bigger, lab-bench type
enclosure but they seem to be the same electronics as the Koolertron unit.
Performance, control locations etc...
Mine seems to be well build, very tiny SMT parts, solder mask, silk
screened part ID's etc.  A few "cons" - I agree with Mike that a battery
powered option would be great, it comes with a 5 Volt 2 Amp wall wart - so
it does consume some power (I did not measure draw.)  . Also, the 2
supplied BNC-Alligator test cables both had intermittent connections in the
crimped BNC connectors.  Junk, but the unit otherwise seems to be well
made.  Comes with a disc/USB cable for external computer control but I have
not tried it as yet.

In addition to providing a crystal substitute, it is also useful for
testing receivers, but would need external attenuators to get signals down
to the microvolt range.. A nice feature is it can sweep from Freq X to Freq
Y in time Z which is handy for sweeping IF amplifiers/filters... It does go
down to audio freqs for testing AF gear..  I try to avoid buying ChiCom
stuff if I can, but at $120 I made an exception and took a chance.  My
LM-14 is certainly "Kooler" but so far, so good..
Thanks again to Dave for alerting me to it...
73,
Tim
N6CC

On Mon, Apr 13, 2020 at 8:11 AM Ian Wilson <ianmwilson73 at gmail.com> wrote:

> Hi Tim,
> The Koolertron unit sounds very useful. Are there any reviews (or tech
> specs) online?
> I'm interested in a couple of things:
>   - what's the frequency generation technology (DDS or synthesis / if DDS,
> how many bits and what spurious levels)
>   - can the device be remotely programmed (e.g. think of using it as a
> VFO, controlled from a separate processor)
>
> 73, ian K3IMW
>
> On Sun, Apr 12, 2020 at 2:17 PM Tim <timsamm at gmail.com> wrote:
>
>> So, David, which one of those available on Amazon are you using? The
>>> Koolertron 60 MHz
>>> job, or another one? It is kinda hard to tell from your photo.
>>>
>>> Ken W7EKB
>>>
>> ----------------------------
>>
>>> Hi Guys - I have the Koolertron DDS, the 60 MHz option.
>>>
>> I'm not familiar with the VHF ARC-5 radio design offhand but I assume
>> Dave is using the DDS in lieu of a crystal to drive the R/T oscillator
>> circuits.  I would guess those utilize multiplier chains.  So I guess
>> driving a multiplier chain would best function with an input already rich
>> in harmonics, unlike a pure sine.  So in that application square waves rich
>> in 3rd harmonics, or pulses in general makes good sense.  As a drive source
>> for an HF MOPA transmitter (or receiver LO) a sine works well. Thanks Dave
>> - you should be getting a commission!  A pretty handy piece of test gear...
>> (my LM-14 is giving me the Stink Eye !)
>> 73, Tim
>> N6CC
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