[RFI] Tiny SA Ultra with DXE Flag and Preamp?

[Pete Smith N4ZR]

This was very interesting - the TinySA Ultra sounds like a great tool. 
Checking online, I was surprised to find it for sale for as little as 
$70 (Karagas), and as much as $140 (Rbay).  In this era of unauthorized 
cloning, I'm wondering if there is a way to identify a good one.

73, Pete N4ZR

On 9/15/2023 11:03 AM, Don Kirk wrote:
> Hi Dave and gang,
>
> The DXE preamp gain is approximately 30 dB (with its attenuators turned
> off) until about 35MHz and then the gain drops like a rock above that point
> so overload from VHF and above stuff is normally not an issue.  Also down
> on 160 meters the gain of the portable flag is -63 dBi and gets lower as
> you go lower in frequency so this naturally helps attenuate strong AM
> broadcast stations.  On 30 MHz the portable flag gain is -19 dBi.
>
> I just ran a quick test with my TinySA Ultra with its LNA on and the DXE
> preamp inline and on with no attenuation selected and the AM filter turned
> on and the strongest AM broadcast station was a station running 5 KW and
> 9.4 miles from my house on 1260 KHz and it measured -55 dBm.  Strongest
> signal received between 200 kHz and 5.3 GHz with DXE preamp AM filter
> turned on was -40 dBm and it was from a shortwave broadcast station on
> approximately 13.6 MHz.  To prevent internally generated spurious emissions
> on the TinySA Ultra I try to keep signal levels below -25 dBm.  I also ran
> a self test on my TinySA Ultra after the above tests and it passed with
> flying colors.
>
> The bottom line to avoid overload from AM broadcast stations when using the
> TinySA Ultra with its LNA on when using the DXE preamp is to make sure the
> DXE preamp AM broadcast filter is turned on but even in my tests today at
> my QTH having the AM filter turned on was not necessary (also a good idea
> to have the TinySA Ultra attenuator set to Auto).  I measured the AM
> broadcast station on 1260 KHz at -70 dBm using just the TinySA Ultra with
> its LNA on when connected directly to the portable flag (DXE preamp not
> connected) and it measured -37 dBm with the DXE preamp inline and on with
> its AM filter turned off which is still well below the overload point on
> the TinySA Ultra.  Therefore unless you are very close to a high power AM
> broadcast station or another very close in transmitter / source of RFI,
> overload of the TinySA Ultra with its LNA on and the DXE preamp inline and
> and on with the AM Filter selected is really not as likely as one might
> think.  I would not have the TinySA Ultra LNA on unless needed to see a
> very weak signal, but this is normal regarding any receiver I'm using as I
> also switch in attenuators as needed to keep the signal of interest under
> the full scale reading of the S meter on my receiver as an example.
>
> Just FYI, and 73,
> Don wd8dsb
>
>
> On Fri, Sep 15, 2023 at 8:43 AM David Eckhardt<davearea51a at gmail.com>
> wrote:
>
>> With the preamp you purchased with the Flag antenna and the preamp built in
>> and selectable within the TinySA Ultra, you should have enough
>> gain/sensitivity to well overload the TinySA, unless you live in the middle
>> of nowhere with no cell coverage, no TV, no FM, no daytime AM radio,
>> and......  Yes, those places still exist here in the west.
>>
>> Dave - WØLEV
>>
>> On Thu, Sep 14, 2023 at 2:21 AM Jim Miller<jim at jtmiller.com>  wrote:
>>
>>> I've got a TinySA Ultra and recently purchased the DXE Flag by WD8DSB and
>>> Preamp. I'm wondering if the combination will be adequately sensitive or
>>> should I use some other receiver?
>>>
>>> Thanks
>>>
>>> Jim ab3cv
>>> _______________________________________________
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>>>
>>
>> --
>>
>> *Dave - WØLEV*
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