Hi
I'm new to radio listening and have no specific area that interests me
more than any other - at the moment. I'm using an RSP1A SDR receiver.
So, that being the case, what does the panel think of something like the
wideband discone described as: RADIOWORLD HF DISCONE 0.05 TO 2000 MHZ
ANTENNA?
Most other discones seem to start at about 25MHz. Can this radioworld
one really extend down to 50kHz, and usably so?
Ta.

In article , Grumps wrote:

It's a discone with a vertical element on top -- the vertical element
provides coverage (such as it is) up to about 25 - 50 MHz, where the
discone proper takes over.

Older editions of the RSGB VHF/UHF handbook have good sections on
discones, the how and why, and how to build them. Check your local
library.

The good news -- yes, discones can be wideband. And lots of folks cheat
on the low end by adding a vertical element (some times, a vertical
element with inductive base loading; this one says it uses a helical
trapped wire element inside that fiberglass thing on top).

The bad news -- very little "gain" (over isotropic). Also, the take-off
angle of the radiation pattern (the angle of maximum sensitivity)
increases with frequency.

Having a pretty flat response (in the discone portion at least) they're
good for transmitting in discone frequencies; I use one on the 144 and
440MHz ham bands transmit-receive as well as receive only for ADS-B (at
1090MHz). If you want to try tricks like that, look at the Comet
CF-413B Duplexer which splits the signal into a low-pass (1.3 - 460
MHz) and high pass (840NHz - 1.5GHz). Outside of the flat discone
response portion though, expect transmit VSWR to be highly variable
(and not it a good way). Limit TX power to a few watts or you're likely
to let the magic smoke out of that vertical element and it's attempt at
impedance matching.

And then there's the care and feeding of a your SDR... The RSP1A has a
set of built-in bandpass filters, which is good news. Your typical $20
SDR is a very wideband device with no to little filtering on the front
end, which makes it prone to overload, especially when you connect an
external antenna with any view of the sky.

You might start looking for low-pass and bandpass filters, such as
those made by Mini Circuits, to tame front-end overloading.

Bottom line, discones can be fun, and useful, if you understand what
they can and cannot do.

Hi
I'm new to radio listening and have no specific area that interests me
more than any other - at the moment. I'm using an RSP1A SDR receiver.
So, that being the case, what does the panel think of something like the
wideband discone described as: RADIOWORLD HF DISCONE 0.05 TO 2000 MHZ
ANTENNA?
Most other discones seem to start at about 25MHz. Can this radioworld
one really extend down to 50kHz, and usably so?
Ta.

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