F-connector or SMA - which is best?
Posted: Fri Jul 17, 2015 8:48 pm
In my opinion changing to an SMA connector was not a good idea. Yes it puts it in line with other SDRs but what about the cable you are forced to use with it.
RG58 or RG 59 has as a loss quoted around 6 dB per 100 ft at 100 MHz - and is the cable you would use with an SMA connector. BTW there are a couple of nice videos on Youtube showing you exactly how to fit both male and female crimp-on connectors.
WF100 satellite cable - has a typical attenuation of 6db per 100 metres - one third the loss - and is the one you would use an F-connector with.
Myself - if I buy an SDR with an SMA connector I will use and SMA/F connetor adapter. But what about the fact that RG58 is 50 ohm impedance and WF100 is 75 ohm - or that most professional/amateur radio equipment is 50 ohm and consumer electronics including FM is 75 ohms.
The sma connector might be better at higher frequencies but RG58 cable loss is horrendous
What effect will feeding SDR Play with a 75 ohm impedance have. If you try and work out a bandpass filter using the on-line calculators you get entirely different results in terms of the capacitance and inductance you need when you change the characteristic impedance.
It is a veritable mine-field.
RG58 or RG 59 has as a loss quoted around 6 dB per 100 ft at 100 MHz - and is the cable you would use with an SMA connector. BTW there are a couple of nice videos on Youtube showing you exactly how to fit both male and female crimp-on connectors.
WF100 satellite cable - has a typical attenuation of 6db per 100 metres - one third the loss - and is the one you would use an F-connector with.
Myself - if I buy an SDR with an SMA connector I will use and SMA/F connetor adapter. But what about the fact that RG58 is 50 ohm impedance and WF100 is 75 ohm - or that most professional/amateur radio equipment is 50 ohm and consumer electronics including FM is 75 ohms.
The sma connector might be better at higher frequencies but RG58 cable loss is horrendous
What effect will feeding SDR Play with a 75 ohm impedance have. If you try and work out a bandpass filter using the on-line calculators you get entirely different results in terms of the capacitance and inductance you need when you change the characteristic impedance.
It is a veritable mine-field.