An option to add a pan-adapter to my IC9100 lead to the purchase of a PAT V 9100 kit. This kit is developed from a design by Dave G4HUP SK. The tap boards (see http://huprf.com/huprf/pat-board/) are high input impedance unity gain amps intended to tap from IF and HF tuned circuits in a range of transceivers. Following Dave’s sad passing last year the HupRF kits and Website have been transferred to and managed by SDR-Kits (David KD2C https://kd2c.com ).
The PAT V 9100 is a design aimed to extend the tap to four points in the front end of an IC9100 to a single PAN Adapter port.
Figure 1- PAT-V-9100 Module
When the kit was assembled and installed (extensive detailed instructions provided), it was time to ask for a check of connections and the operation of the radio with the PAT fitted.
When asked to review the installation, George VK4AMG was pessimistic about the TAP connection points on the top of the VHF through SHF tuned circuits and doubted if a two stage source/emitter follower could have the required frequency response (to 1300 MHz). The connection from the TAP point to the module by 30+ cm of RG142 coax cable (20+ pF) and the shield connected only at one end also caused concern about detuning and coupling noise into the front end of the receiver.
A PIN diode switch has been added to the front end of the PAT amplifier in attempt to provide automatic selection of the active receiver in the IC9100. There is no termination on the PIN diode switch. A normal value would be conflict with the supposed high impedance of the amp. The DC voltage at most of the recommended tap points is the tuning voltage for the front-end bandpass circuits and is insufficient to provide effective switching of the PIN diodes with or without a terminating resistor.
Figure 2 and 3 show the frequency response of the PAT-V-9100 module with and with biased PIN switches.
The Hi-Z section is useful as an IF/RF tap to about 50 MHz. As an RF tap for a VHF / UHF radio it is a 20+ dB attenuator. With any detuning of the RF tuned circuits due connection of the PAT-V-9100, the radio sensitivity is degraded and an externally connected SDR may only show signals of S7 or better.
Figure 2PAT-V-9100 Freq Response - No bias on input diodes
Figure 3- PAT-V-9100 One input diode forward biased, Others reverse biased
George has previously used applied PGA-103 LNA modules (Minikits PGA-103 LNA kit https://www.minikits.com.au/PGA-103-Amplifier?search=pga-103 or eBay “0.05-4GHZ Low Noise Amplifier LNA RF Broadband Amplifier 23dB High Linearity 5V”) with a SMD attenuator / splitter inserted in the VHF / UHF RF cables or internally in the IC910 23 cm module. In addition to providing a high-performance TAP point, the LNA lifts the performance of the IC910H receiver. The options for combining four of these modules to cover the IC9100 bands are being evaluated and will be published when this project is complete.
Figure 4- LNA and attenuator providing a 23cm TAP in IC910H
Testing
has taken place by VK4AMG, with a full report on his findings will be
posted the new year.