Martin Eastburn wrote:

Balms maybe - RF transformers. But impedance matching
is still going on with various T, L, H, patterns.

Many have LNA's in them as well. I have a dual myself.
It is an active RF circuit you have to plug in. It downshifts
the frequency, combs out the noise, boosts the signal and then
impedance matches two outputs from a single input.

Many versions. Many of them are etch on substrates.


Martin, I've spent my life working in RF. From AM Broadcast to well
past 11 GHz. First of all, a BalUn coverts from balanced to
unbalanced. In TV that also included an impedance transform from 300
Ohm balanced to 75 Ohm unbalanced. A simple broadband transformer, and
often on a plastic core in the early days. TV splitters with equal
outputs are all two port directional couplers to provide at least a 20
dB backmatch, and that is considered a low grade device. At one time I
was testing samples from dozens of vendors to either qualify them for
our CATV systems to purchase, or remove them from our AVL. Most two way
splitters were a simple ferrite core with three identical windings, one
to each port, with a few PF cap between the two outputs in an attempt to
improve the backmatch. What Harold described wasn't an active device,
so there was no reason to bring them up. A MiniCircuits MAR, ERA or any
of their other 1 GHz MMICs can give you 10 to 20 dB of gain with a
decent match for under a buck. Avango (HP) and several other companies
make similar parts, in the same price range. If you have plenty of
excess gain to burn, you can use resistive dividers. OTOH, you add more
noise to the overall system gain.

A LNA is a 'Low Noise Amplifier' and it does not 'downshift the
frquency'. A LNB or LNC dows convert the frequency, for Sat TV. The
LNC is used with an LNA to form a LNB and there are multiple types of
converters. Block, tunable or phaselocked block where a pilot carrier is
sent up the coax with the DC power, ant the output comes back on the
same coax.

My RF gear is in use by NASA, NOAA, the ESA and on board the ISS.