LNA QRO with built-in bypass relays for 6m 2m and 70cm bands

Update from 2020-01-28

VSWR Bypass
VSWR Bypass

The following changes have been made:
– Added power injector for power through the feeder. SWR (TX mode) not worse than 1.1 for 2m and 1.2 for 70cm;
– Added the function of switching the LNA input from the antenna to a load of 50 Ohm. Useful for checking the ratio of antenna noise to load noise. Switching is carried out by applying increased power to 16 V (briefly, for the duration of the measurement). The operating voltage of the LNA is 12 V. To prevent overheating of the LNA, do not leave 16 V for a long time!
– LNA 70cm QRO with SAW filter now, compensation inductances and power injector.


This LNAs are suitable when operational conditions requires huge RF power bypass. They are quite simple in installation – just connect the unit into the feeder.

Unlike our low-bypass solutions this lineup doesn’t contain RF VOX. For RX/TX switching you should use the sequencer, for example this one.

LNA 2m QRO schematics

LNA 2m QRO schematics revision from 2020-10-02
LNA 2m QRO schematics revision from 2020-10-02

LNA 2m QRO schematics archive

LNA 2m QRO schematics revision from 2018-05-12
LNA 2m QRO schematics revision from 2018-05-12
LNA 2m QRO schematics
LNA 2m QRO schematics

LNA 2m QRO layout

LNA 2m QRO layout revision from 2020-10-02
LNA 2m QRO layout revision from 2020-10-02

LNA 2m QRO layout archive

LNA 2m QRO layout revision from 2018-05-12
LNA 2m QRO layout revision from 2018-05-12
LNA 2m QRO layout
LNA 2m QRO layout

LNA 70cm QRO schematics

LNA 70cm QRO schematics revision from 2020-10-02
LNA 70cm QRO schematics revision from 2020-10-02

LNA 70cm QRO layout

LNA 70cm QRO layout revision from 2020-10-02
LNA 70cm QRO layout revision from 2020-10-02

LNA 2m QRO AFC graph is shown on Fig. 3.1. BW(-3dB) < 15MHz. Supression of the broadcast FM band is not worse than -50 dB.

Amplitude-frequency response of LNA 2m QRO
Fig. 3.1 Amplitude-frequency response of LNA-2m-QRO
Amplitude-frequency response of LNA 6m QRO
Fig. 3.2 Amplitude-frequency response of LNA-6m-QRO

NF measurements results Fig. 3.3 Fig. 3.4 (provided by RU3T)

LNA 2m QRO NF measurements results
Fig 3.3 LNA 2m QRO NF measurements results
LNA 70cm QRO NF measurements results
Fig 3.4 LNA 70cm QRO NF measurements results

Conclusion

QRO series LNAs are allow to use PAs with high RF power without additional RF relays. Considering the fact that NF < 0.6dB is usually enought (for 2m band), LNA-2m-QRO is pretty universal solution. For 70cm NF < 0.8dB is OK for Tropo and Contest QSO. For 70cm EME QSO we still highly recommend to use our EME solutions for this band (based on SAV-541+ or ATF-531P8) with additional RF relays.

We had more than 30 working QRO units for 2m and 70cm bands when this article was created. However you should consider some protective measures – reducing the transmitter’s RF Power while this LNAs are used with antennas that have a bad VSWR (greater than 1.5).

Warning!
Working with antennas, that have a bad SWR (> 1.5) may lead to failure of the RF relays.

List of changes:
– instead of PGA103, ATF53189 used;
– LNA 70cm QRO switched to SAW filter design.

LNA 2m QRO N-female

LNA 2m QRO N-female

Specifications
Name LNA-2m-QRO-N-female
Based on ATF-53189
Pmax TX bypass 1000 Watt
Gain > 24 dB
NF < 0.4 dB at 144 MHz
OIP3 36 dBm
Filter BW (-3 dB) < 15 MHz
P input (max) 24 dBm
Supply operation 12 V & 300 mA
Impedance 50 Ohm
RF connectors N-female
Weight 0.25 kg
Package contains
1 x LNA-2m-QRO-N-female

LNA 70cm QRO SAW filter N-female

LNA 70cm QRO SAW filter N-female

Specifications
Name LNA-70cm-QRO-SAW-N-female
Based on ATF-53189
Pmax TX bypass 800 Watt
Gain > 20 dB
NF < 0.4 dB at 432 MHz
OIP3 36 dBm
Filter BW (-3 dB) < 20 MHz
P input (max) 24 dBm
Supply operation 13.8 V & 300 mA
Impedance 50 Ohm
RF connectors N-female
Weight 0.25 kg
Package contains
1 x LNA-70cm-QRO-SAW-N-female

General inquiries: e-mail logo sales@vhfdesign.com
Technical support: e-mail logo us4ici@vhfdesign.com

Check the stock availability – here
Request for an assembly – submit this form

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