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Got an older HR2510? Older Cobra 29/25?

HR2510 - Just disconnect the Final and Driver - and keep the Pre-Driver in Place...- you can make a simple "signal beacon" since the HR2510 uses LOW-Drive (meaning Audio Modulation starts at the Mixer and only goes up from there) low-level modulation. For TX (carrier + Audio) You just solder a jumper wire from the Pre-Driver Q124 amp - the output leg of C127 (the HOLE of the one lead that heads towards the DRIVER) to the output leg of the Final at the Tank Coil Circuit in this case the MRF477 is BEC - so you'd have to solder to the OUTPUT or Collector side of the part - just unsolder all legs of Driver and Final to protect them.

And at TP1 you'd have 10;69MHz and at TP304 you'd have 38MHz for anything you wish (IF Imaging)

• So, sending carrier wouldn't be a problem, nor would it be any serious problem of any sort, as your selection of tone can be a simple squeal from feedback to help with audio peaking (SINAD - stuff)

Cobra 25/29 series can be used to help with goofy IF signal tracing - BUT they are not able to send signal because of the High-level Modulation section you're bypassing.

Cobra 29

• Remove JP36 - solder jumper wire from Output leg lead of R58 to center Foil pad of Final Collector - again, unsolder all legs of Driver and Final to protect them - this is for TX (10.240 + 16~17MHz IF - NO OFFSET)
• - for the output mixer of the 29 is at the connection between C85/R62 and R61 for TX, sometimes it's labeled TP4.
• But RX has IF and is off by 455kHz - that is at C16 and R17 - that tie is TP5 on some radios and it's labeled. (TP5) (others it's TP3) - this is for those that need IF signal OFFSET of 455kHz

Cobra 25

• The RX of the 25 is like that of the 29 (as usual) (the 10.240 and 16~17MHz IF conversion Down-Mix) so look for TP3 silkscreened on the board or the junction bare lead of R6 and C10 - again off by 455kHz
• Output Mixer of the 25 uses TX, it's at TP4 and is the junction tie of R46/R47 and C53.
• You might want to remove the JV17 jumper (the one that goes to the Driver and Final Collectors' from the Audio transformer)
• But to use a buffered TX output (50Ω ohm stuff) Locate R43 10Ω resistor - lift its output leg and solder jumper wire to output tank circuit at Finals Collector (center solder pad) again, unsolder all the legs of Driver and Final to protect them.

The process above simply places the radio in a low-power mW mode for TX straight for other radio RX to "hear". The power is in Milli-watts (1/100th - of a watt) - but is useful for measuring and alignments as needed.

Especially when you DO NOT know of the IF condition of a radio

• - so the IF signal from a WORKING radio also has an offset - you can use TP3.
• - is it possible if you try and probe and you get a signal?
  • - tells you that you may have a radio that has IF or main Xtal working because the IF signal image to make 455kHz is used from the radios own Xtal. (Depends on where you get your IF from, usually TP3 is the 455kHz OFFSET)
  • - while TP4 has to be in TX Mode to get it.
• Can be a great diagnostic tool to help you realign another radio if the IF of the radio under test needs to be checked or verified.

So, in a way, you can kill (er - FIX) one radio - but you still need two to tango.