HiTec Laser 4, FM

[BobR]

Being that I am not up to date on Hitec Surface radios I find myself lost when it comes to finding what I need or knowing what to look for. I have a Hitec Laser 4 radio and need to get several sets of crystals for both the TX and RX but they need to be 75mh dual conversion FM. Would someone explain "dual conversion" to me and tell me who has the best selection at a reasonable price. Thanks,
Bob

[PaulP]

Dual conversion refers to the receiver and the manner in which it processes the signal. The carrier frequency is 75 MHz. In a single conversion radio, the electronics convert this frequency to 455 KHz. In dual conversion equipment, it is first converted to around 10MHz then again down to the 455 KHz.

The advantage is it allows for greater selectivity in the signal. The disadvantage is it adds cost to the system. Better performance generally comes with a price penalty.

The crystals are different on the receiver since dual conversion requires a different output frequency.

Regarding pricing, I have had good luck with a company in Madison, WI called Hobby Horse. They are a stocking HiTec dealer, offer great pricing and quick delivery. Their link is http://www.hobbyhorse.com/

Another thing to remember is crystals are generally specific to the brand of radio - ie Futaba crystals won't work in a HiTec radio. Also your radio needs to be built/tuned to 75MHz. You can't take a 72MHz radio and convert it by just changing the crystals.

Paul

[BobR]

Thanks Paul, that helps me to understand how the radio works. I like the new digital radios but also want a knob to adjust jib trim. The radio I have (Laser 4) doesn't have a knob either but it doesn't make sense to me to buy a new system when you still end up with no knob. Let me ask this, does the TX crystal also have to be dual conversion or just FM? Hobbyhorse has pretty good prices in their cystals. I will have to call them and order several sets.

Bob

[s vernon]

Some of my understandings about radios, rcvrs and crystals. Please correct me if I am wrong.

The receiver determines single or dual conversion. The radio can use either one, but if the rcvr is dual conversion then the radio crystal must be dual conversion and vise versa.

You can use say a Futaba rcvr with a Hitec radio as long as the rcvr crystal is Futaba and the radio crystal is Hitec.

On the early 3 channel Hitec radios some local guys were using Futaba Skysport rcvrs so they could get away from the Hitec single conversion blues. They used proper brand crystals as I have described above.

I know I should not post this without double checking the site, but here goes nothing. I'll check it tomorrow.
One thing that I was surprised to see stated on the Futaba website: Aircraft frequencies are broken into high and low because of the very large number of channels, and it is possible for those aircraft guys to use any frequency crystal and get good performance. What I mean by that is the radio and rcvr might be tuned for the lowest low channel or say the highest high channel, but it is possible to fly with the frequency at the opposite end of the low or high spectrum, but must be low in low and high in high. They said nothing about legalities, just performance. This makes me wonder if we land frequency guys can stray far from our tuned frequency and get good performance since we have fewer channels than the aircraft guys. No info about that on the Futaba website.

Scott

[BobR]

Whats funny is that as I checked on the site that Paul told me about they listed single or dual for the RX but not for the TX. This is what made me think that the main differenec was in the RX. As long as they both were either AM or FM. They don't even show a dual conversion for the TX...now I am really confused. I just sent hobbyhorse an email asking them if both needed to be "Dual Conversion" or just the rx.

Bob

[BobR]

OK, here is the poop....the dual conversion is only on the rx end, not the TX which is why they don't offer dual conversion crystals for the RX. Boy, I'm glad that is straightened out!!!

[John Ebell]

Bob if you want just a transmitter with the additional channel for your jib trim the Hitec Laser 6 is a good deal. If you already have everything, ie Crystals and receiver from Hitec check, out this guys Ebay store for a Laser 6. http://stores.ebay.com/Toms-RC-Simulato ... eZl2QQtZkm I have bought two from him. Hint here: if you buy a transmitter it comes with a crystal. Specify a particular frequency you would want and also order the Receiver crystal at the same time. You save on shipping and his prices for them aren't bad either. That way you build yourself up alternate frequencies. You know with so many guys going to 2.4 GHZ it opens up so many more frequencies for us old fashioned users.

Good Luck,
John Ebell

[PaulP]

It sounds like everyone is on track.

Dual conversion is specific to the receiver only.

Yes you can mix transmitters with receivers, to a certain amount. If it is a FM radio, it must match which side of the signal is used. You can mix HiTec and Futaba, but not Airtronics or JR (as I recall) However the crystal brand must still match the receiver, ie: HiTec radio must use HiTec crystal.

It is also a good idea to only move about 6 channels on either side of the original frequency. Beyond this amount, the radio will probably still work but you may experience a loss of range or interference problems. If the radio was originally tuned to channel 74, you could go up to 80 or down to 68 and still be within tolerance. Outside that range, you take your chances. Since we operate at such shorter ranges than the airborne guys, we can get away with a little mismatch. Their application is a little more critical.

Some of the guys are modifying their radio, changing one of the channel sticks for a potentiometer (knob). This is easily accomplished with a soldering iron and a 5K pot. I think Reichard is doing it for guys. Maybe he'll chime in on this. You can accomplish this on any 3 or more channel radio.

Paul

[kahle67]

Not me, I am a dummy when it comes to electronics.

Reichard Kahle
Charleston, SC

[BobR]

John,
That is a good price but I am saving all my pennies for a J-boat so I will have to wait for a while. I ordered 4 sets of crystals and will just wait for them to arrive. The radio I got with the boat has a pot installed and I am hoping that its the trim for the jib.
Rich, I'm with you,110,220 and 440, I'm fine, give me something small and electronic and I'm lost.

Bob

[BobR]

Paul,
I ordered my crystals for Hobby horse on the 17th. I still haven't gotten them and when I called to check on my order they told me that they were waiting for them to come from Hitec. I guess they don't stock many so I don't know when I will get them. Prices are good, same price for TX and RX crystals.

Bob