SDRplay Community Forum

Hi-Z Port delivers as advertised using 20M longwire directly connected (No 9:1).
Port A using a Scanking 0.05 to 2000 Mhz discone really delivers the goods! Not quite up to the longwire/Hi-Z although under certain conditions it can actually sometimes improve on that (of course everyone's situations differ).
Port B using the above discone does not perform anything like as well below about 4 Mhz as when connected to Port A.
In fact, connected to Port A the discone receives a great signal on 198 Khz, whilst on Port B virtually no or only a weak and corrupt one.
I have an active min-whip on order that I intended to connect to Port B, but am wondering whether in fact I would be better to connect this to A given the differing performances.
Any suggestions as to why there should be such differences between Port A an B would be very welcome (Bias T not in use).

Hello Paul,
Port B has worse low frequency roll-off when compared to port A because of the presence of the bias-T circuitry. This effect is present whether the bias-T is enabled or not.

Sincerely

SDRplay Tech_Support

Thank you for a prompt and clear explanation; it will help me going forward.

Replacing the RF blocking coil on the bias feed with a proper sized one (larger) would cure this... Not sure why a bias-t is included in the RSP since its need is antenna dependent and the bias=t belongs on the antenna side of an external antenna switch. With some circuit board hacking it might be possible to remove the bias-t and its signal degradation.

I suppose antenna B input is intended for VHF and above, where masthead pre-amps are more frequently used to overcome coax losses. Most of us would not use an antenna amp on HF.