Standard dongles come with a small, often black, short antenna which threads onto a small magnetic base, which provides the connection to the coax, on its way to the dongle.
Does anyone happen to know the measurements (pitch and diameter) of the threaded part, and what, if any, standard it follows? Metric? Non-metric?
I don’t have a suitable thread gauge, and have yet to get a good match through trial and error.
Thanks
The dongles come in three types.
The latest RTL-SDR and FA Dongle uses the SMA connector.
en.wikipedia.org/wiki/SMA_connector
Nooelec mostly uses MCX
en.wikipedia.org/wiki/MCX_connector
There are a few models that use the F connector.
en.wikipedia.org/wiki/F_connector
@jonhawkes2030
I think yxespotter’s question does not pertain to the antenna input connector on the dongle. It pertains to the stock antenna supplied with the generic dongle (black). The thread he refers to is the thread on the brass bolt on top of the magnetic base, to which the whip screws. Please see sketch below:
abcd567,
Re-reading it, it looks like your are correct.
That thread could be any size as there are a large number that make them.
I have several but have no idea what size they are.
there is absolutely no permutation of the supplied whip that can exceed the performance of such, barring a properly constructed Collinear.
@k5ted
Couple of months ago, I purchased this $3.38, 1090 Mhz wire collinear antenna, but it proved to be much inferior than the trimmed stock antenna shown in my previous post.
Just now I finished quick comparison of two antennas, the stock antenna, whip cut to 52 mm vs wire collinear. In the message rate graph below, the left 50 minutes are for 52mm stock whip, and right 10 minutes are for wire collinear.
The difference is self speaking.
https://farm8.staticflickr.com/7002/26494128403_6b475db3a5_z.jpg. https://farm8.staticflickr.com/7741/27029662331_60a551d541_z.jpg
That looks more like it would act as a center loaded whip than a collinear whip. Would be interesting to put it on the bench and see where it actually resonates.
Yes, you are right. It better falls in category of coil loaded antenna rather than the collinear (due to very short length of whip between coil & feed point). The coil here acts as loading coil rather than phasing coil of a collinear.
Here is another antenna loading coil from begening of last century 
Would be interesting to put it on the bench and see where it actually resonates.
A full antenna test bench … a dream not come true 
, but I will sure setup one when I win a lottery or hit a jackpot
Not having the actual antenna here in my hands, but comparing to the other 1/4 wave whip in the picture, it could possibly be some sort of half-wave over quarter-wave design of collinear, but just doesn’t look right somehow…
Looks like my $US9 antenna from amazon.
amazon.com/1090Mhz-Antenna-C … detailpage
I suspect it isn’t actually designed for 1090Mhz.
Fine print seems very strange.
Your observation about dimension of antenna is nearly correct. I am not at home now. When I will reach home, I will measure and post its dimensions.
but just doesn’t look right somehow…
The loading coil (to improve SWR) at the base is missing.
The coil in this antenna is between two sections (1/2 wavelength & 1/4 wavelength) and is a phasing coil. A 1/4 wavelength hairpin shaped stub could also do this job, but is inconvenient due to its physical shape. A coil is commonly used, and the hairpin stub is rarely used.
Please see this post about 1/2 over 1/4 (=3/4):
A 3/4 λ Collinear Groundplane Antenna
.
