Difference between the SP and SP-S preamps

In our daily work we often hear the question from our customers: what is the difference between the preamps of the SP series and those of the SP-S series?

From the outside, the devices look the same, the same housing and the same connections.

Let´s take a look and compare the technical specifications:

Technical data	SP 200	SP 200 S	SP 70	SP 70 S
Frequency range [MHz]:	144-146	144-146	430-440	430-440
Noise figure (20°C) (NF) [dB]:	0,7	0,8	1,0	1,0
Gain (S21) [dB]:	8-18	18	13-22	25
Max. switching capacity with RF VOX PEP [W]:	500	500	300	250
Max. switching capacity with RF VOX CW/FM/FT8 [W]:	750	750	500	500
Insertion loss [dB]:	0,04	0,08	0,15	0,25
Return loss when transmitter is active [dB]:	36	38	35	40
Input return loss (S11) [dB]:	42	30	20	27
Output return loss (S22) [dB]:	25	32	26	20
OIP3 [dBm]:	27	32	20	19
IIP3 [dBm]:	9	14	-2	-6
Current consumption [mA]:	250	150	330	190

The technical data of the preamplifiers differ only slightly. Both series can be supplied with power via the coaxial cable or via the PL socket (remote or direct feed). For example, they work perfectly with the ICOM IC-9700, the Yaesu FT 847 and the power amplifiers, e.g. from BEKO. The models of both series also work together with the DCW 2004 B without any problems. With the DCW 2004 B, the power supply is also provided via the coaxial cable, so that no additional cable has to be laid to the preamplifier.

It has to be mentioned that the current consumption is lower and the insertion loss is higher with the S series amplifiers. Different relays are installed in the amplifiers. Genuine Tohtsu coax relays are used in the SP series. Power relays from Panasonic are used in the SP-S series. This explains the different current consumption and insertion loss in the TX case. Another difference between the preamps is that you can only adjust the gain on the SP series. Everything else - like amplifier MMIC or the built-in HF-Vox - are the same for both preamplifiers.

In the end you have to decide for yourself what is more important to you. In any case, both preamplifiers are a very good solution in every VHF/UHF amateur radio station.

If you have any further questions, don´t hesitate to send us an email support@ssb-electronic.de.

73 de Martin Müller, Technical Support at SSB-Electronic