I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots andground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots andground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots andground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
On Monday, October 23, 2023 at 9:28:59 AM UTC-4, LoftusRoadLad wrote:ground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots and
Consider replacing your battery with a Life battery. They are now very reasonable in cost and available from Amazon. Their charged voltage is about 13.8 volts and capacities are about 10ah.You also might consider increasing the size of wire from your battery to the radio, which helps as well, particularly when you are transmitting.
UH
On Monday, October 23, 2023 at 1:20:41 PM UTC-4, Hank Nixon wrote:and ground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
On Monday, October 23, 2023 at 9:28:59 AM UTC-4, LoftusRoadLad wrote:
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots
I had a customer that had that problem with a MicroAir 760. He was running it thru a 1 amp circuit breaker. Radios need at lease 4 amp breakers.Consider replacing your battery with a Life battery. They are now very reasonable in cost and available from Amazon. Their charged voltage is about 13.8 volts and capacities are about 10ah.You also might consider increasing the size of wire from your battery to the radio, which helps as well, particularly when you are transmitting.
UH
Dan
If you are using a 12Volt Sealed Lead Acid (SLA) battery then the issues are that the fully charged voltage is only 12.7V and the output voltage steadily falls as the battery discharges. You might find that even a new SLA battery gives only 12.0Vafter 40% discharge. Some radios start struggling to transmit with under 11.5V.
I'd start by measuring the battery discharge rates with an ammeter whilst the radio is in receive mode and then transmit mode. If these are high, then look at what other equipment or faults is drawing current.13.7V fully charged, drop quickly to around 13V where they remain for the majority of the time discharging before suddenly giving up useful output. These characteristics are ideal for gliding but there is a perceived safety risk due to the chemistry,
The most common size of glider battery seems to be 151 x 65 x 95mm. Lead Acid in this size is usually 7AmpHour. A similar size Lithium Iron Phosphate battery is available as 12 AmpHour, and is significantly lighter. Lithium batteries start at around
If you do run a lead acid battery, then you have to be very careful about 'voltage drop', which is the inefficient dissipation of power resulting in low voltage at the radio. Some tips have already been given but here's my thoughts:should be not less than 18 AWG diameter.
- All cable has resistance. Minimise cable lengths and reduce the gauge (ie increase diameter). The cable from the battery to the main switch is usually the longest length of wire in the circuit and thus can be a major cause of voltage drop. It
- The radio draws a high current so all components in radio circuit have bigger voltage drop. The radio should have its own dedicated sub-circuit ie dedicated CB/fuse. Most radio manufacturers say use minimum 18AWG tinned stranded copper to the radio.
- Minimise joints and connectors as these are a possible cause of high resistance ie voltage drop.
- If using screw connector blocks, use ferrules to avoid loose strands and ensure max contact with screw terminals.
- If a cable joint in the radio circuit is required, use crimps rather than solder.
- Circuit breakers have a high resistance, especially low Amp rated CBs. The smaller the CB rating the higher the voltage drop. Fuses have lower voltage drop.
- Check the condition of the master switch. A switch has internal resistance and thus voltage drop. This is usually very small but can be degraded by dust or moisture penetration, age or not up to the required DC amp specification.
I have a FL-760 radio. Before I fly I charge the battery for at least6 hours (it's virtually brand new). Connected, it shows around 12.7
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots andground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
On Monday, October 23, 2023 at 9:28:59 AM UTC-4, LoftusRoadLad wrote:ground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots and
Consider replacing your battery with a Life battery. They are now very reasonable in cost and available from Amazon. Their charged voltage is about 13.8 volts and capacities are about 10ah.
UH
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots andground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
On Monday, October 23, 2023 at 9:28:59 AM UTC-4, LoftusRoadLad wrote:ground crew my transmissions are initially clear but then fade to garble or screech. Reception is fine. Any thoughts?
I have a FL-760 radio. Before I fly I charge the battery for at least 6 hours (it's virtually brand new). Connected, it shows around 12.7 volts initially. When I transmit the voltage drops sometimes to around 11.4 volts. According to other pilots and
Ok, so I hear it's a 9AH LifePo battery. Radio is good for about 2 hours.
My questions to OP....
What all is in the glider?
Transponder?
Radio (yes)
Flarm?
Electric vario?
Strobe?
The 2 hours, is that just "on time" or transmit time? If running a full panel but little transmit time, it's likely a failing battery, small wires, poor connections.
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