Due to their very nature, HF mobile antennas must be physically short compared to their wavelength. In order for them to hear and radiate effectively, they must also be properly matched to the 50 ohm antenna port on your HF rig.
由于車(chē)載短波天線(xiàn)本身的特性，與短波的波長(zhǎng)相比，這些天線(xiàn)本身必須非常短。為了能有效的接收和發(fā)射，這些天線(xiàn)還必須和短波設(shè)備上50歐姆天線(xiàn)端口正確匹配。
The impedance found at the feed point of HF mobile antennas varies all over the place. The reason for this is the variance in the mobile environment itself. The size and type of vehicle, the ground area it covers and even the space between the body and the Earth (ground) all have an affect on impedance. You may find that the best impedance match you can achieve results in is a 3:1 SWR at resonance!
在車(chē)載短波天線(xiàn)的饋電點(diǎn)發(fā)現(xiàn)的阻抗分布四處。原因是汽車(chē)內(nèi)外環(huán)境本身的差異造成的。車(chē)輛的大小和類(lèi)型、地面區(qū)域覆蓋、甚至身體和地球之間的空間(接地)都對(duì)天線(xiàn)的阻抗產(chǎn)生影響。你會(huì)發(fā)現(xiàn)3:1 駐波比值居然是最好的阻抗匹配!
Many mobile HF antennas are naturally between 10 ohms and 36 ohms at resonance. With 10 ohms at a 50 ohm feed point the resulting SWR is 5:1! Likewise, 36 ohms yields a 1.4:1 SWR. Matching at 1.4:1 isn’t too bad, but 5:1 is definitely an issue. Fortunately, there is a convenient solution to the problem.
很多車(chē)載短波天線(xiàn)自然地在10歐姆和36歐姆之間的共振。10歐姆的天線(xiàn)在50歐姆饋點(diǎn)產(chǎn)生5:1的駐波比 ! 同樣，36歐姆產(chǎn)生1.4:1 的駐波比。在1.4:1的匹配不是太壞，但5:1的駐波比絕對(duì)是個(gè)問(wèn)題。幸運(yùn)的是，現(xiàn)在有一個(gè)方便的解決問(wèn)題的辦法。
DX Engineering Dual Impedance Antenna Transformers DXE-MM-1
DX Engineering 雙阻抗天線(xiàn)變壓器 DXE-MM-1
DX Engineering MM-1 Dual Impedance Antenna Transformers are ideal for adjusting the impedance mismatch in your HF mobile! When the natural resonant impedance of the antenna is at 30 ohms or below, the MM-1 mobile unun can provide the needed match. With a 50 ohm input, it provides a 25 ohm port and a 12.5 ohm port to facilitate mobile HF matching.
DX Engineering MM-1雙天線(xiàn)阻抗變壓器適用于在移動(dòng)通信時(shí)調(diào)整阻抗失配!當(dāng)自然共振天線(xiàn)的阻抗等于或低于30歐姆時(shí)，MM-1可以提供所需的匹配。50歐姆的輸入，它提供了一個(gè)25歐姆和12.5歐姆的端口來(lái)促進(jìn)移動(dòng)車(chē)載天線(xiàn)的匹配。
Let’s say that your antenna analyzer indicates an antenna impedance of 22 ohms. Your SWR without an MM-1 would be 50/22 or 2.27:1. That’s enough to cause considerable power rollback in most modern HF rigs. Using the MM-1 25 ohm port, your SWR would be 25/22, or 1.14:1. That’s a very significant improvement!
假設(shè)你的天線(xiàn)分析儀顯示天線(xiàn)阻抗22歐姆。未安裝MM-1的駐波比將是50/22或2.27:1。這足以引起相當(dāng)大的功率反射到短波設(shè)備上。利用MM-1 25歐姆接口，駐波比將達(dá)到25/22,或1.14:1。這是一個(gè)非常顯著的改善!
Many hams are using antenna analyzers to adjust mobile HF antennas. When a mismatch is indicated at resonance, a DX Engineering MM-1 unun can solve the problem!
許多火腿使用天線(xiàn)分析儀調(diào)整車(chē)載短波天線(xiàn)。在共振失配時(shí)，DX Engineering的MM-1 unun 可以解決這個(gè)問(wèn)題!
Price:$119.95
價(jià)格：119.95美金
source：http:///achieve-better-efficiency-with-your-hf-mobile-antenna/ via DXengineering Blog
